Tables for the determination of minerals by means of their physical properties, occurrences, and associates

Kraus, Edward Henry · 1911 · Historical

The successful determination of minerals at sight depends upon the ability to make quick and accurate distinctions between the physical properties

This 1911 document, Tables for the determination of minerals by means of their physical properties, occurrences, and associates, is preserved in the Mountain Man Mining Library for research and reference. Original source: archive.org.

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Tables

For The

Detekmination Op Minerals

published the

McGroTv- Hill Book- Company

Ne'v Yorlt

fiuccMaora to thcDookDeparimenU oF the

McGrawPubUahing Company Hill PuULshin Company

Electrical World The Engineo'ing and Mining Journal

Enneenng Record and ITie Enneer

Electric luilwy Journal American Mocninijt

MetallurcaJ and Clieinical Engineering

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Tables

Determination Of Minerals

By Means Of

Their Physical Properties, Occurrences, And Associates

EDWARD HENRY KRAUS, Ph. D.

And Walter Fred Hunt, A. M.

McGRAW-HILL BOOK COMPANY 239 WEST 39TH STREET. NEW YORK

a BOUVERIE STREET, LONDON, E. C.

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' Cdllebe J

Copyright, 1911 - McGraw-Hill Book Company

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The successful determination of minerals at sight depends upon the ability to make quick and accurate distinctions between the physical properties, occurrences, and associates of the several minerals which may be suggested by the luster, color, form, streak, and hardness, especially, of a given specimen. As a result of extensive experience in the laboratory and field, luster and color have been made the fundamental basis of these tables, further subdivisions being introduced by the streak and hardness. Minerals with similar physical properties are thus grouped together, aiding the student materially to acquire the necessary facility to make rapid distinctions.

The tables include 250 of the most common minerals, classified into three groups, which may be designated as (1) very common, (2) common, and (3) not common, but important. The display given to the name of a mineral indicates at a glance in which of the above groups it has been placed. Page references to several textbooks on mineralogy will be found of great convenience when more detailed descriptions are desired than obviously can be given in determinative tables.

\Vc have drawn freely upon all possible sources but are under especial obligations -to Weisbach, Ktockmann, Crosby, and Eakle, whose tables were constantly before us.

MlNBBALOGICAL LaBORATOST, EDWARD H KrAUS,

University of Michigan, „, '

February, 1911. WALTER F. HuNT.

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Table Of Contents.

Preface v

Introduction. — Physical Properties — Luster, Color, Streak, Hardness, Crystallization, Structure, Cleavage, Parting, Fracture, Specific Gravity, Tenacity, Transparency, Taste, Odor, Feel or

Touch, Magnetism x

Glossary 7

General Classification and Analytical Key 14

Minerals with Metallic Luster 16

Minerals with Non-metallic Luster 68

Index 249

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Introduction.

Physical Properties.

The physical properties of moat importance in the determination of minerals at sight, without the aid of blowpipe or chemical reactions, will be described briefly. AH terms given in the introduction or used in describing minerals in the tables are defined in the glossary, page 7.

Luster. — The luster of a mineral is the appearance of its surface in reflected light, and is a property of fundamental importance in the rapid determination of minerals. The luster and color of minerals may usually be easily recognized at first sight.

Lusters may be divided into two large groups: metallic and non-metallic. Tlie metallic luster is indicative of metals and is exhibited by minerals which are opaque or nearly so. All other lusters may be designated aa non-metflllic, some of these being described as vilreoiix or glassy, adamantine, resinous or greasy, pearly, silky, dull, earthy, splendent, and so forth.

Color. — The color of a mineral is one of the first physical properties to be observed. Some minerals have a fairly constant color, while in others it may vary greatly, due to the presence of pigments, inclusions, or other impurities. The terms used in describing the various colors need no explanation.

Streak. — This is the color of the fine powder of a mineral and is one of the most important physical properties for the determination of minerals. Although the color of minerals may vary greatly the streak is often fairly constant. The color of the streak may be determined by crushing, filing, or scratching. The usual and most satisfactory method, however, is to rub the mineral on a piece of white, unglazed porcelain, the streak plate. The ease or difficulty with which the streak is obtained is to some extent indicative of the hardness of a mineral.

Hardness. — -The resistance offered by a mineral to abrasion or scratching is termed hardness. It is indicated relatively in terms of Mohs's scale, which consists of ten common minerals arranged in order of increasing hardness, as follows:

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2 Introduction.

Beryl, 7.5 to 8 in hardness, is often substituted for topaz in the above scale.

Substances, scratched by and which in turn scratch some one member of the scale, are said to have the hardness assigned to that member. In determining the hardness of a mineral the scratch made should be short as possible, not over 1/4 inch, and care exercised to distinguish between a scratch and a chalk mark, the latter being easily removed by rubbing.

The determination of the approximate hardness is greatly simplified by using the finger nail, copper coin, and the knife blade, which possess the following values :

Finger nail, up to 2.5 Copper coin, up to 3 Knife blade, up to 5 . 5.

Since the majority of the minerala are less than 6 in hardness, this simplified scale is of great convenience in determining the approximate hardness in the laboratory and field.

In the tables which follow on page 14, minerals have been divided into three groups based upon the hardness of two very common minerals, calcite and feldspar, thus : (1) 1 to 3, softer than or as hard as calcite; (2)

3 to 6, harder than calcite but not harder than feldspar; (3) over 6, harder than feldspar.

Crystallization. — Minerals are described in the tables as occurring in crystals or masses. Crystals are bounded wholly or in part by natural planes and may be divided into six groups called the crystal systems. Massive minerals are either crystalline or amorphous.

The crystal systems are characterized by their axes.

Cubic System. — Three equal and perpendicular axes. Some forms are the cube,* octahedron, dodecahedron, tetrahcxahedron, tetragonal trisoctahedron, hex octahedron, tetrahedron, and pyritohedron.

Hexagonal System. — Four axes, three of which are equal and horizontal, intersecting at 60°. The fourth is vertical, perpendicular to, and either longer or shorter than the horizontal axes. Common forms are prisms, bipyramids, pyramids, basal pinacoid, rhombohedron, and scalenohedron.

Tetragonal System. — Three axes, two of which are equal, horizontal, and perpendicular to each other. The third axis is vertical, perpendicular to, and either longer or shorter than the horizontal axes. The important common forms are prisms, bipyramids, pyramids, basal pinacoid, and bisphenoid.

For a fuller description of Home of the following Mrm? see OieBlossary, poge7; consult any standard textbook' ' "

Introduction. 3

Orthorhombic System. — Three unequal and perpendicular axes. The axis extending from front to rear is the brachyaxia, the one from right to left the macroaxis, while the third is the vertical axis. The names of the cryst alio graphic forms often indicate the axis to which they arc parallel. Some common forms are prisms, bipyramids, pinacoids, and domes.

Monodinic System,— Three unequal axes, two intersect obliquely, while the third is perpendicular to them. The axis from front to rear, held inclined to the observer, is the clinoaxis, the one from right to left the orthoaxis, while the third is the vertical axis. The common forms are prisms, hemipyramids, domes, hemidomes, and pinacoids. The specific names often indicate the axis to which the forms are parallel.

Triclinic System. — Three unequal and inclined axes, designated as in the orthorhombic system. Common forms are tetrapyramids, hemi- , hemidomes, and pinacoids.

Structure. — Most minerals occur in masses without any definite crystal outline and are said to bo crystalline or amorphous. Crystalline aggregates or masses are made up of closely packed crystalline grains of irregular form, while amorphous substances are entirely devoid of crystallinity. Some of the more common and important terms used in describing the structure of massive minerals are: adcular, botryddal, bladed, capillary, deavable, columnaT, compact, cryptocrystalline, Jibrous, foliated, lamellar, mammillary, phanerocrystalline, reniform, and stalactitic. These and other terms relating to structure are defined in the glossary, page 7.

Cleavage .M any minerals split or separate easily along definite planes. This property is called cleavage, and is often very conspicuous and highly characteristic. The planes along which the separation takes place are parallel to possible crystal faces and so designated. Thus, octahedral cleavage signifies that the splitting takes place parallel to the faces of the octahedron. The manner and ease with which cleavages are obtained can be indicated by such terms as, perfect, imperfect, distinct, indistinct, easy, and so forth.

Parting. — This is a false cleavage and usually takes place parallel to twinning planes.

Fracture. — The fracture of a mineral refers to the character of the surface obtained by breaking crystalline substances in directions otherthan those along which cleavage or parting may take place, or amorphous substances in any direction. The various fractures are described as, conchoidal or shell-like, even, uneven, hackly, spliniery, or earthy.

Specific Gravity. — The specific gravity of a solid substance is its weight compared with the weight of an equal volume of water. The specific gravity of minerals can be determined most conveniently by means of the

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Inthoduction.

recording Jolly balance* recently devised by Professor F. H. Kraus. This balance consists of the square upright tube T to which the fixed vernier M and the movable graduated scale X are attached, as shown in the accompanying figure. T contains a second tube Z which can be moved by the milled-head A. The vernier N is attached to Z by the arm E. Screw B controls the rod H,, movable within the tube Z. From R the spiral S and scale pans C and D are suspended, the thin wire rods W and V connecting the spiral

and pointer

the

pans with which, set in jewelled bearings, swings freely in front of a small circular mirror.

To determine the specific gravity of a mineral, it is necessary that the graduated scale X, verniers M and N, and the pointer P all be at zero, the lower scale pan D being immersed in water. P is brought to the zero point by being made to coincide with the mark on the mirror, the adjustment being accomplished by the screw B. A fragment of the mineral is now placed on the upper pan C, and the elongation of the spiral noted by again bringing the pointer P to the zero position. This is done by turning the milled-head A, and moving the tube Z and graduated scale X upward. After the zero position is obtained the scale is clamped by the screw Y. The reading at M gives obviously the elongation of the spiral due to the weight of the mineral in air. The fragment is now transferred to the pan D under water, care being taken to avoid air bubbles adhering to it. The pointer P is again, for the third time, brought to the zero position by moving the tube Z and attached vernier N downward by turning the bead A. The reading at N indicates directly the loss in the elongation of the spiral, due to the immersion of the fragment in water. If the weight of the

mporten of

Introduction. 5

specimen in air be represented by W, the reading at M, and the loss of weight when immersed in water by L, the reading at N, we have,

W

Specific gravity -

The advantages of this balance over others in common use are that the elongations of the spiral for the weight of the specimen in air and loss of weight when immersed are recorded, and further only two readings and a simple division ar necessary to obtain the specific gravity, which is generally accurate to within a few units of the second decimal. The whole determination ought not to require more than two minutes.

Tenacity. — Under this heading is included the behavior of a mineral when an attempt is made to break, cut, hammer, crush, bend, or tear it. The following well-known terms are used: elastic, flexible, JHable, brittle, inelaBlic, tough, sectile, -malleable, and ductile.

Transparency. — This is the ability to transmit light and is of minor importance in the determination of minerals by means of their macroscopic physical properties. Substances through which objects can be easily and distinctly seen are said to be transparent, those through which no light appears to pass, even in very thin layers, opaque. Between these extremes we may distinguish subtransparent, transluceM, and subtranslucent substances.

Taste. — Minerals soluble in water or the saliva generally possess a characteristic taste, which may be described as astringent, saline or salty, alkaline, pungent, metallic, cooling, bitter, acid, or sour.

Odor. — Some minerals give off characteristic odors when breathed upon or heated by being rubbed, scratched, or pounded. These odors are arsenical or garlic, sulphurous, bituminous, fetid, and agriUaceous or clay-like.

Feel or Touch. — The impression one receives by handling or touching a mineral is called the feel or touch. It is designated as smooth, greasy, or Boapy, harsh or meager, or cold.

Magnetism. — Comparatively strong magnetism is shown by a few iron-bearing minerals, their powders or small fragments being readily attracted by a magnet. A convenient method to test the presence or absence of magnetism in a mineral, without crushing it, is to suspend a small horseshoe magnet from the finger so that it may swing freely and then bring the specimen under consideration close to the magnet. If the specimen is magnetic the magnet will be deviated from its vertical position, the amount of the deviation indicating roughly the relative strength of the magnetism.

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Glossary.

The glossary contains all terms given in the introduction or used in describing minerals in the tables.

Adcular — needle-like.

Acute — sharply pointed.

Adamantine luster — tike that of the diamond, or oiled glass.

Aggregate — mass, cluster, group.

Alkaline taste — like that of soda.

Alluvial — relating to deposits made by flowing water.

Amorphous — devoid of crystallinity.

Amygdaloid — igneous rock containing small cavities, which are filled entirely, or in part, with minerals of secondary origin.

Arborescent — branching, tree-like.

Astringent taste— causing contraction or puckering.

Basal — parallel to the basal pinacoid.

Basalt — basic igneous rock, dark and compact,

Bipyramld — two pyramids placed base to base,

Blsphenoid — four-sided form of the tetragonal system, each face being an isosceles triangle.

Bladed — elongated and flattened, like a knife blade.

Botryoldal — closely united spherical masses, resembling a bunch of grapes.

Bracbypinacold — form with two faces in the orthorhombic or triclinic systems, parallel to the brachy and vertical axes.

Brittle — crumbles under knife or hammer, cannot be cut into slices.

Capillary — hair-or thread-like.

Cellular — porous, like a sponge.

Chatoyant— having a changeable, undulating, or wavy color or luster.

Clastic — made up of fragments.

Clay— fine soft, aluminous sediments that are plastic.

Cleavable — capable of cleaving or splitting in definite directions.

Cleavage — property of many crystalline substances of breaking or splitting in definite directions, yielding more or less smooth surfaces.

Clinopinacold — form with two faces in the monoclinic sytem, parallel to the clino and vertical axes.

8 Gl0S8Ary.

Columnar — long thick fibers, often parallelly grouped.

Compact — closely or firmly united.

Complex crystals — highly modified, having many crystal forms or faces.

Concentric — spherical layers about a common center, similar to layers of an onion.

Coochoidal — curved, shell-like.

Concretion — rounded mass formed by accumulation about a center.

Concretionary — formed as a concretion.

Confused — indistinct, jumbled together.

Conglomerate — sedimentary rock, composed of rounded fragments, coarse or fine.

Contact mineral — formed under the influence of an igneous intrusion.

Crested — tabular crystals arranged in ridges.

Cruciformn the form of a cross, cross-shaped.

Cryptocrystalllne — finely crystalline, revealed only under the microscope.

Crystal — substance bounded, entirely or partially, by natural plane surfaces.

Crystalline — having crystal structure, but without definite geometrical form.

Crystallization — process of solidification in the form of well developed crystals, or in crystalline masses.

Cubic system — see page 2.

Cubical — with the form of a cube.

Cyclic — repeated twinning yielding circular forms.

Dendritic— branching, fern-like.

Dlchroism — property of exhibiting different colors by transmitted light when viewed in two directions.

Disseminated — scattered through a substance.

Divergent— radiating from a center.

Dodecahedral — pertaining to the rhombic dodecahedron, a form with twelve faces in the cubic system.

Domatlc — relating to a dome, a horizontal prism.

Drusy — rough surface due to a large number of small, closely crowded crystals.

Ductile — capable of being drawn into wire. Ductile substances are also malleable and sectile.

Dull luster — not bright or shiny.

Eartby — without luster, dull.

Efflorescence — thin crust or coating, often powdery.

Elastic — resumes original position when displaced.

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Gl088Ary. 9

Eruptive rock — formed by the solidification of a surface flow of molten rock. Often used aa a synonym of igneous.

Etched — corroded.

Felted — fibers closely matted.

Ferruginous — containing iron.

Fibrous — consisting of slender fibers or filaments.

Fissure — crack or crevice.

Flexible — capable of bending without breaking, and does not resume original position when the force is removed.

Fluorescence — property of showing different colors in reflected and transmitted light.

Folia — having the form of thin plates or leaves.

Foliated — in plates or leaves which separate easily.

FoESlllferous — containing or composed of fossils.

Fracture — refers to surface obtained when breaking in a direction other than parallel to cleavage or parting.

Friable — easily crumbled or reduced to powder.

Furrowed — deeply striated, grooved.

Gangue — associates of more valuable minerals or ores.

Globular — spherical or nearly so.

Gneiss — laminated or foliated metamorphic rock consisting usually of quartz, feldspar, and mica.

Granite — coarsely crystalline igneous rock, consisting usually of quartz, feldspar (orthoclase), and mica or hornblende.

Granular — consisting of closely packed grains, either coarse or fine.

Guano — excrement of sea fowl.

Habit — development or form of crystals.

Hackly — rough surface, covered with sharp points.

Hardness — resistance offered to abrasion or scratching. See page 1.

Hemlmorphlc — having different planes about the two ends of a crystallographic axis.

Hexagonal sjrstem — see page 2.

Hexoctahedron — form of the cubic system having forty-eight faces.

Hopper shaped — cavernous and tapering, square funnel shaped.

Hygroscopic — property of absorbing moisture from the atmosphere.

Igneous rock — one formed by the solidifaetion of a molten mass from within the earth.

Impregnated — finely disseminated and intimately mixed with rock.

Impressed— marked by pressure, indented.

Inclusion— foreign material enclosed within a mineral.

Incrustation — crust or coating on another substance.

Inelastic — not elastic-

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Interlaced

, r intertwined, confused,

Interwoven ' '

Iridescence — showing play of colors, usually due to thin film or coating.

Klmberlite — altered, very basic igneous rock, consisting essentially of serpentine, olivine, augite, pyrope; sometimes diamond-bearing.

small, thin plates or layers, curved or straight.

Lamellar — consisting of lamelhe or laminae.

Lava — molten rock, especially surface flows; also applied to the solidified product.

Lenti cular — lens-sh aped .

Limestone — rock composed essentially of calcium carbonate, calcite.

Luster — manner in which the surface reflects light.

Macroplnacoid — forrn with two faces in the orthorhombic or triclinic systems, parallel to the macro and vertical axes.

Macroscopic — visible to the unaided eye, opposed to microscopic.

Malleable — capable of being flattened by hammering.

Mammillary — rounded mass, larger than that of a grape.

Massive — without definite crystal form; either crystalline or amorphous.

Metallic luster — similating a metal and exhibited by minerals which are opaque, or nearly so, and quite heavy,

Metalloidal — having the appearance of a metal.

Metamorphlc rock — one that has been altered by heat, pressure, liquids, or gases, so as to render its texture either crystalline or schistose.

Meteorite — mass of stone or iron which has fallen to the earth from outer space.

Micaceous — composed of very thin plates or scales, like those of mica.

Modified, highly — consisting of a large number of crystal forms or faces.

Monoclinlc system — see page 3.

Mottled — spot ted .

Multi-colored— having many colors.

. . rounded mass of irregular shape.

Nugget — rounded, irregular lump, especially of a metal. Ocherous — earthy, and usually red, yellow, ~or brown in color. Octahedral — pertaining to the octahedron, eight-sided form of the cubic system.

Oolitic — rounded particles the size of fish-eggs.

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opalescent — with milky or pearly reflections.

Opaque — will not transmit light even through thin layers or edges.

Oithopinacoid — form with two faces in the monoclinic system, parallel to the ortho and vertical axes.

Orthorhombic system — see page 3.

Parting — false cleavage, usually the result of twinning.

Pearly — similar to the luster of the mother of pearl.

Peat— dark brown to black substance, formed by the partial decomposition of vegetable tissue in marshes.

Pegmatite — very coarse grained acid igneous rock, consisting essentially of quartz, feldspar, and mica.

Peildotite — very basic igneous rock, composed largely of olivine and augtte.

Pbanerocrystalline — crystals or coarsely crystalline.

Phonolite — compact extrusive igneous rock, consisting essentially of orthoclase, nephelite, and pyroxene.

Plnacoidal — relating to forms with two planes, parallel to two or more cryatallographic axes.

Plsolltic — composed of small, rounded masses, the size of peas.

Pitchy — resembling pitch.

Placers — sands and gravels containing minerals of economic importance.

Plfutlc — capable of being molded or shaped.

Plates — broad, relatively thin masses.

Platy — consisting of plates.

Plumose — feathery.

Pocket — cavity in a rock, often filled with minerals.

Prismatic — elongated parallel to one of the crystallographie axes, usually the vertical axis.

Pseudo — false.

J 1, ( possessing the geometrical form of another mineral.

Pungent — sharp, biting.

Pyramidal — pertaining to the pyramid, a form which usually intersects three crystallographie axes.

Pyritohedron — form of the cubic system with twelve, five-sided faces.

Rectangular — intersecting at 90°.

Refraction, double — yielding two refracted rays.

Reniform — large, rounded masses, kidney-shaped.

Resinous — luster of resin, greasy,

Retlculatedfibers crossing like a net.

Rhombic — diam ond-shaped.

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Rhombohedral — relating to the rhombohedron, a form of the hexagonal system, with six faces intersecting at angles other than 90°.

Rosette — simulating a rose.

Saline— salty.

Sandstone— sedimentary rock conaiating of consolidated sand.

Scalenohedral — relating to the sealenohedron, a twelve-sided form of the hexagonal system, each face being a scalene triangle.

Scaly — consisting of scales.

Schiller— peculiar bronze-like luster.

Schist— metamorphie rock with foliated or parallel structure, splitting easily along certain planes.

Seam — narrow vein.

Sectile— capable of having slices cut off.

Semi-opaque — between opaque and transparent.

Shale — laminated sedimentary rock, consisting of hardened muds, silts, or clays.

Sheai-llke — resembling a sheaf of wheat.

Silky — luster of silk, due to fibrous structure.

Skeletal — pertaining to crystals with incomplete development of their faces, often with cavernous appearance.

Slate — dense, fine grained metamorphie rock, which splits easily into broad, thin layers or sheets.

Splendent — very bright by reflected light.

Splintery — breaking into splinters.

Stalactltlc — cylindrical or conical masses resembling icicles.

Stalky — consisting of long, stout fibers.

Stellate— -radiating from a center producing star-like forms.

Streak — color of fine powder, usually obtained by rubbing the mineral on unglazed porcelain.

Structure — see discussion page 3.

SubadamantiDe — im perfectly adamantine.

Subconcholdal — imperfectly conchoidal.

Sublimation — direct solidification from a vapor.

Submetallic — imperfectly metallic.

Syenite— granular igneous rock, commonly consisting of orthoclase, and hornblende or biotite.

Tabular— flat, tablet-like.

Tarnish' — -thin film formed on the surface when exposed to air and <lifferent in color from that of the fresh fracture.

Tenacity — see discussion page 5.

Terminations — faces on the end of a crystal.

Tetragonal system — see page 2.

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Glossary. 13

Tetragonal trisoctahedron — form of the cubic system with twentyfour trapezohedral faces.

Tetrahedral — pertaining to the tetrahedron, a four-sided form of the cubic system.

Tetrahezahedron — form of the cubic system with twenty-four triangular faces.

Tough — not easily broken.

Translucent — when light passes through, but objects can not be seen distinctly.

Transparency — refers to the amount of light passing through a substance.

Transparent — when sufficient light passes through the substance so that objects may be distinctly seen.

Trap — dark basic, fine grained igneous rock.

Tricllnic system — see page 3.

Trillings — iiitergrowth of three crystals in a symmetrical manner.

Twinned — crystals consisting of more than one individual, arranged in a definite manner.

Twins — symmetrical intergrowth of two crystals.

Variegated — with different colors.

Vein — crack or fissure, partially or completely filled with mineral matter.

Tfltreous luster — like that of glass.

Warty — small, rounded masses resembling warts.

Waxy — luster of wax.

Zonal — in zones or layers.

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GENERAL CLASSIFICATION A. HDfERALS WITH METALLIC LUSTER

Color of mineral

HudneM Pagp

. Dark gray or black. .

2. HetalUc white or metaiUcgraj

4. Brass, bronze, or copper red '

White, gray, green, red, brown, „ , -,

, f 1 to 3

Black I „

r 1 to 3

Metallic white or steel gray „

mi / lto3

Black „ „

Gray, brown, or yellow 1 to 6

Black Over 3

Gray, red, or yellow 1 to 3

Black Over 3

White, gray, green, red, brown I ftf:

Black 1 to6

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And Analytical Key.

B. Minerals With Hoh-Hetallic Luster

Color of mlneTBl

Hordnem Page

Dark gnj or black . .

2. Pink, red, or red violet . .

. Green, blue, or blue violet. .

Uncolored, white, or light gray.

Piok, red, brown, or yeUoi

Uncolored, white, or light gray.

Uncolored, white, or light gray.

Red, brown, yellow or black . ,

Uncolored, white, or light gray.

1 to3 3 to 6 Over 6

I to 3 3 to 6 Overs

1 to3 3 to6

Over 6

5. Colorless, white, or light /

Uncolored, white, or light gray, .

A. Ubbrals With Metallic Luster

StreakWhite, gray, green, red, , or yellow

Name, Compoaition, and References

Cryatalliiation

Structure Luster

Crystals -C I Transparency

Massive — M 1

Never in crystals M— Compact, fibrous, lamellar

Subraetallic Black Waxy Brownish

Translucent black

, Danon Panaiu

Wad MnO„ H,0, etc.

Amorphous 7 Dull

H — Earthy, sometimes Submetallic with globular struc- Opaque

Brownish

black Black

Amorphous

Dull

Black

M— Compact, fibrous;

Opaque

Brownish

C, H, 0, etc.

black

3S

woody structure

REHATrTE, variety

Hexagonal

Metallic

Iron black

Specuiar %

ron ore

C— Thin tabular, often

Splendent

Dark steel

Pe,0,

in parallel position M— Scaly, micaceous,

Opaque, to

translucent

gray

Se, 334.

platy, foliated Monoclinic

Submetallic

Black

C— Tabular, with hex-

Pearly

Brownish

agonal or rhombohe-

Opaque to

black

dral habit

transparent

Greenish

black

scales

Pyniyrite

Hexagonal

e-mail, complex,

Metallic Adamantine

Dark lead

hemimorphic, rare M— Compact, dissemi-

Opaque to transparent

nated, bands, crusts

Silver

Cubic

Metallic

Dark gray

C — Small, often distorted

Opaque

black a

Ag

H — Grains, scales, plates, twisted hair-or wirelike forms

expos

others

New York; K

1. DARK GRAY OR BLACK HI COLOR HardneBB 1 to 3

ClumcteriBtics a ad

Aaeociatee

fingers; may be

Easily indented by Soger nail. Reaembles impure wax. Greasy feel. In sandstones and shales. With petroleum and coal.

2.6 White 3, Grayish

2.6 Cherry red 3. Purplish red

2.6 Silver white 3. Light lead gray

F— Conchoidal

Brittle to tough

C— None, but distinct parting F— Uneven Brittle to elastic

C — Basal, perfect, conspicuous

Tough, laminie of fresh biotite very elastic

C — Imperfect F— Conchoidal Brittle

F— Hackly Malleable, ductile

Very soft varieties soil fingers. Apparently very light and floats on water, due to porosity. Usually adheres to tongue. With psilomelane, pyrolusite, siderite, limonite.

More or less carbonized plant remains. May disintegrate on exposure. Jet, compact, coal black variety with resinous luster.

Bright, shiny scales, often loosely compact; foliated or micaceous masses. In metamorphic rocks or as sublimation product around volcanoes.

Easily recognized by structure, highly perfect cleavage, and elasticity. Important constituent of many igneous and metamorphic rocks — granite, syenite, gneiss.

Frequently as gray or dark red bands, known as dark rvby silver ore. With proustite; in veins with other silver minerals and galena.

Color and streak darken on exposure. With silver, lead, arsenic, cobalt, and nickel minerals — argentite, pyrargyrite, proustite, smaltite, galena; also fluorite, calcite, barite.

d PatBOus, UiDekicy. Revised Edition

A. Hiherals With Metallic L0Ster

Streak— White, py, green, red, brown, or yellow

Crystallization

Structure

Luster

Color

References

Crystals -0 Massive

Transparency

Tetrahedrtte

Cubic

Metallic

Dark steel

Cu,Sb,S,

C— Tetrahedral, often

Opaque

gray

highly modified

Iron black

KrauB. Daoa, Parsons

Cubic

Pitch-like

Pitch black

C— Octahedral, rare

Submetallic

Brownish

U0„ U0„ PbO, etc.

M — Botryoidal, columnar

Dull

black

curved lamellar, gran

Opaque

Greenish

ular, compact; appar-black

ently amorphous.

AUbandite

Cubic

Submetallic

Iron black

C— Rare

Dull

MnS

M— Granular, compact

Opaque

Siderite

Hexagonal

Brownish

C— Rhombohedral, curv-

Dull

black

ed or saddle-shaped,

H — Cleavable, granular, compact, botryoidal,

Opaque to translucent

Black

rarely fibrous

Cubic

Submetallic

Black

Resinous

Yellowish

ZnS

often very complex

Opaque to

black

M— Compact, cleavable,

Brownish

fine or coarse gran-black

ular

Hanganite

Orthorhombic

Iron black

C — Columnar, prismatic,

Dark steel

MnO.OH

vertically striated ; often in groups or bundles

Opaque

gray

stalactitic

♦Cuprite

Cubic

Adamantine

Reddish black

C —Octahedrons, dodeca-

Dull

Black

Cu.O

hedrons, alone or in

Translucent

combination

to opaque

M— Granular, earthy

Uacommou color.

:y

1. Dark Gray Or Black In Color

Hardnesa 3 to C

Fracture — F Tenacity

Specific Gravity

Reddish brown

C— Indistinct

Crystals have characteristic tet-

F— Uneven Brittle

rahedral habit. Sometimes coated with chalcopyrite. With. sphalerite, galena, boumonite, chalcopyrite, siderite.

Dark browD

F— Conchoidal, un-

Pitch-like appearance and frac-

Olive green

Brittle

ture important. Fresh material is hard and heavy. With ores of lead, silver, and bismuth; also thorite, orthite, fergusonite.

0!ive green

C— Cubical, not con-

Color may tarnish brownish

spicuous

black. Streak characteristic.

F— Uneven

With rhodochrosite, galena, py-

Brittle

rite. argentite, sphalerite.

Yellowish

C— Rhombohedral,

Distinguished from sphalerite by

brown

perfect, conspic-

F— Conchoidal

Brittle

curved crystals and rhombohedral cleavage. In ore deposits; beds and concretions in limestones and shales. With pyrite, chalcopyrite, galena, tetrahedrite, cryolite.

S.6

Dark brown

C— Dodecahedral,

Color and streak vary with im-

Yellowiah

perfect, usually

brown

conspicuous

stone. With galena, chalcopyrite.

Grayieh

F — Conchoidal Brittle

pyrite, barite, fluorite, siderite, rhodochrosite.

Reddish brown

C-— Brach ypinacoida 1 ,

Altera easily to pyrolusite, hence.

Blackish

perfect

surface may give black streak.

brown

F— Uneven

Brittle

With other mangauiferoua minerals; also barite, calcite, siderite.

Brownish red

C— Indistinct

Easily recognized by associates.

Dirty brown

F— Uneven Brittle

Usually with other copper minerals—malachite (green), azurite (blue), chalcocite and melac-

A. Mbtebals With Metaluc Luster

Streak— White, gray, green, red, brown, or yeUow

Name, Composition, and

Structure

Luster

References

Crystals

Massive -M

Transparency

Tetragonal

Submetallio

Black

C— Square prisma with

Vitreous

Brownish

bipyramida

Opaque to

black

M™

M— Compact, dissemitranslucent

Kmus. Dana,

nated

Goethite

Orthorhombic

Brownish

C— Small, thin tabular,

Translucent

black

FeO.OH

needle-like; parallelly grouped or in scaly, fibrous, velvety crusts

to opaque

Black

B3. 349,

H— Reniform, stalactitic

Monoclinic

Submetallio

Black

C— Wedge-or envelope-

Vitreous

Brownish

shaped when disseminated, tabular or

tached

Opaque to translucent

black

H — Compact, lamellar

C— Always pseudo-

Metallic

Black

Dull

Brownish

atter pyrite, marcasite, siderite M— Compact, stalactitic. botryoidal, reniform; often with internal, radial fibrous struc-

Opaque

black

ture

Hausmannite

Tetragonal

Metallic

Black

C— Acute pyramidal, cyc-

Greasy

Brownish

Mn,MnO.

hc twins not uncom-

Opaque

black

M — Granular, compact

Monoclinic

Submetallic

Brownish

C— Long fibrous, bladed,

Resinous

black

stalky; often diver-

Translucent

Black

gent, without good

to opaque

terminations

H — Compact, lamellar.

granular

Uaoomman color.

1. Dark Gray Or Black Ih Color

Cleavage - Fracture - Tenacitjr

Specific

Gravity

Light orange Dark brown

C— Priamatic, not

conspicuous F— Conchoidal Brittle

Yellow Yellowish browi

n perfect

F— Uneven, splintery Brittle

While Gn,y

C— Prismatic F— Conchoidal Brittle

Dark brown to black thorite

sometimes contains nucleus of OTongite, yellow to orange in color. Thorite believed to be deeompoBed oraugite.

Usually with other iron ores; in cavities in hematite or limonite. Crystals and cleavage distinguish it from limonite.

Generally in crystals. With feldspars, pyroxenes, amphibolea, chlorite, scapolite, zircon, apatite.

F — Conchoidal,

splintery Brittle

Often with black varnish-like sui face, passing into the soft, yellow earthy or ocherous variety. With pyrite, hematite, magnetite, goethite, siderite. Pseudomorphs after pyrite verycf

s.

Chestnut brown

C— Basal, perfect

Steep, horizontally striated, octa-

F— Uneven Brittle

hedral-like bipyramids and complex twins. With manganese minerals— pyrolusite, psilomehematite

.

Yellowish brown

Structure, cleavage, and specific

Greenish gray

perfect, conspicu- Brittle

gravity important. Compare wolframite. In quartz veins,

galena, tetrahedrite.

A. Hhierals With Hetallic Luster

Streak— Vbite, gray, green, red, brown, or yellow

Name, Composition, and

References

Cryatallization Structure Crystals -C Massive— M

Luster Transparency'

Wolframite

Monodinic Submetallic Dark gray

C — Tbick tabular, short Metallic Brownish

columnar, often Opaque black

Moeea laie Iron black

Dana, Pareooa M — -Bladed, curved 1am-

Monoclinic Sub metallic

C — Long prismatic, prism Vitreous

Silicate of Ca, Mg, Fe, Al, etc. angle 124°; often Opaque to

with rhombohedraU translucent

like terminations M — Bladed, fibrous,

Pitch black

Greenish

Adgite

Monoclinic

Submetallic

Pitch black

C — Short prismatic,

Vitreous

Greenish black

Silicate of Ca, Mg,

Fe, Al,

thick columnar,

Opaque to

Browoish

etc.

prism angle 87° M— Compact, granular,

black

m

3S6

S

Orthorhombic

Metalloidal

Black

£

C— Prismatic, tabular.

Pearly

Brownish

rare

Opaque to

black

M— Granular, foliated.

translucent

Greenish black

cleavable aggregates

Amorphous ?

Iron black

M— Botryoidal, reni-

Dull

Bluish black

MnO„ BaO, H,0, etc.

form, stalactitic;

Opaque

Dark gray

smooth surfaces

Heiagonal

Metallic

Iron black

C— Thick tabular.

Brownish

rhombobedral M — Thin plates, granular, compact; disseminated grains;

Opaque

black

pebbles or sand

1. Daic£ Gray Or Black Ot Color

Cleavage — C

Fracture -F Tenacity

C— Clinopinacoidal,

perfect, conspicu-

DistinguiBhed from hueberuite by streak. Powder may be slightly magnetic. With cassitrite, quartz, mica, fluorite, apatite, 8cheelit, molybdenite, huebnerite.

Gray C — Prismatic, perfect,

Grayiali green conspicuouB124''

Grayish brown Brittle YeUow

Simple, pseudo hexagonal crystale and cleavages at 56° and 124° important. Very common and in nearly all types of rocks. With calcite, feldspars, quartz, pyroxenes, chlorite.

Grayish green

C— Prismatic, per-

Crystals usually eight-sided, more

Gray

fect, conspicuous —87° Brittle

rarely tour-aided. Pseudotetragonal, with prism angles of 87° and 93°. Cleavage less distinct than on hornblende. Common in basic eruptive rocks and crystaUine hmestones.

White

C — Brachypinacoida 1,

Copper red iridescence often noted.

Grayish

perfect, conspicuous

F— Uneven

Brittle

due to small tabular inclusions.

igneous rocks; with feldspar (labradorite), olivine, hornblende, pyrrhotite, magnetite.

Dark brown

F— Conchoidal, un-

Often with fine sooty coating of

Blackish brown

even Brittle

nese minerals; limonite, barite.

Dark brown

C — None, partings

Often slightly magnetic. With

Reddish brown

may be noted F— Conchoidal Brittle

hematite, magnetite, apatite, serpentine, titanite, rutiie. Common in black sands.

L.onz=cB>

A. Bcoierals With Hetaluc Luster

Streak — White, gray, green, red, brown, or yellow

Cryatallization

Structure Luster

Crystals — C Transparency

Massive— M

Samahskite

Orthorhombic

Sub metallic

Velvet black

C— Rare

Greasy

Black

M-Compact, apparent-

Opaque

R" -Fe, Ca, U0„ etc.

ly amorphous; dis-

R"'=.Ce, Y, etc.

M™

seminated grains

Kraus, Dana,

Chromite

Cubic

Submetallic

Iron black

Pitchy

Brownish

M — Compact, granular.

Opaque

black

Black

C— Tabular, rare

Greasy

Pitch black

H — Compact, granular,

Opaque to

Brownish

bladed, disseminated

translucent

black

grains

Tetragonal

Metallic

Only in crystals, — py-

Adamantine

Brownish

TiO,

ramidal, tabular;

Opaque to

black

re, 346,

rarely prismatic

translucent

Reddish black

Brookite

Orthorhombic

Iron black

Only in crystals, —py-

Adaraautine

Reddish black

TiO,

Opaque

Brownish

black

prismatic, tabular

Perovskite

Pseud ocubie

Metallic

C — Apparently cubes,

Adamantine

Grayish black

ten striated M — Reniform aggregates.

Opaque

Brownish black

rounded grains Hexagonal

HEMATITE, varieties

Iron black

Specular iro

n ore

C— Pyramidal, tabular.

Dull

Reddish black

Fe,0, Compact

rhombohedral

Opaque

Dark steel gray

H — Compact, granular,

micaceous, columnar, radiated reniform or botryoidal

Reddiah bro? Yellowish brown

L DABE GRAY OR BLACK IV COLOR HanliuBB 3 to 6

Cleavage — C Fracture -F Tenacity

F— Conchoidal,

Specific

Gravity

Splendent luster, conchoidal fracture, and apparently amorphous structure important. With columbite, feldspars.

6.6 Dark brown Grayish brown

6.5 Grayish 6. Brownish gray Pale brown

C — Octahedral, indis-

F — Uneven, conchoidal Brittle

C— Pinacoidal, indis-

F— Uneven, conchoidal Brittle

May be slightly magaetjo. Pitchlike appearance. With serpentine, chrome garnets, zaratite; also in black eands and platinum placers.

Often coated with yellowish or brownish alteration product. Disseminated in the more acid igneous rocks; also in hmes tones. With magnetite, epidote, quartz, feldspars.

B.D

Gray

C— Pyramidal, basal,

Crystals often resemble elongated

White

perfect F— Subconchoidfll

octahedrons. With brookite, rutile, ilmenite, adularia, titanite.

Brittle

gold.

Pale yellowish

C— Indistinct

Crystals may be deeply striated.

brov/n

F— Uneven

Not twinned like rutile. With

Gray

Brittle

rutile, anatase, titanite, ilmenite, adularia, nephelite.

White

C— Cubical, fairly dis-

With chlorite, magnetite, lime-

Grayish

tinct F— Uneven

Brittle

6.D

Cherry red

C— None, parting

Specular iron ore, crystals or

Reddish brown

F— Uneven Brittle

sparkling scales and grains, often with iridescent tarnish; compact hematite, fibrous, columnar, reniform

; martite, octahedral crystals, pseud omorphous after magnetite; argillaceoua hematite, impure from sand, clay, jasper.

A. Minerals With Metallic Lusier

Streak— White, gray, green, rpd, brown, or yellow

Crystallization Structure Cryatala— C Massive— M

Luster

Transparency

Framklihite

Kiaus. 158,

Cubic

C— Octahedrons, alone or

with dodecahedron; often with rounded MoMa edges PoQfl M — Compact, granular, 217 rounded grains

Metallic

Dull Opaque

Iron black

Tetragonal

C— Pyramidal, rare

Vitreous Dull

black

Translucent opaque

Streak — White, gray, green, red, brown, or yellow

HEHATriE, varieties

Specular ire Fe,Oi Compact

Martite ArgilUuxout

Hexagonal Metallic

C — Pyraroidal, tabular. Dull

rhombohedral Opaque M — Compact, granular,

radiated reniform or botryoidal

Iron black Reddish black Dark steel gray

Cubic

Metallic

Iron black

C— Octahedrons, alone

Dull

dron; often with rounded edges M — Compact, granular,

Opaque

16S. 341,

Orthorhombic

Submetallie

Iron black

C — Stort prismatic, tab-

Greasy

Brownish

ular

Dull

black

M— Compact, dissemi-

Opaque

nated

Tetragonal Metallic Iron black

C — PriBmatic, vertically Adamantine Brownish

striated; twinned. Opaque to black

yielding knee-aped translucent Reddish black or rosette forms M — Compact, dissemi-

1. DAR£ GRAY OR BLACK m COLOR

Hoidnesa 3 to 6

Cleavage

Fracture -F Tenacity

Gravity

C — Octahedral, indis-

F— Conchoidal Brittle

Powder frequently alightly magnetic. Diatinguihed by agaociates— wiUemite (yellow to green), incite (red), rhodonite (flesh red), calcite.

6.G Pale brown 6. Dirty brown

F — Conchoidal,

Luster on fresh fracture submetallic, otherwise dull. Less common than columbite. With quartz, lircon, gadolintte.

Reddish brown C — Octahedral, Dark brown tinct

F— <;onchoidal

Brittle

Specular iron ore, crystals or sparkling scales and grains, often with iridescent tarnish; compact hematite, fibrous, columnar, reniform; martite, octahedral crystals, pseudomorphous after magnetite; aTgillaceoua hematite, Impure from sand, clay, jasper.

Powder frequently sUghtly magnetic. Distinguished by associates — wiUemite (yellow to green), incite (red), rhodonite (flesh red), calcite.

6. Reddish brown C — Pinacoidal, n 6.5 Blackish brown conspicuous

F— Conchoidal, u

Brittle

Pale yellowish C — Prismatic, brown ramidal, n

Gray spicuous

F — Uneven Brittle

Fracture surface i descent. With beryl, tourmaline, spodumene, cryolite. Tantalum predominates in tantalite, and specific gravity may be as high as 9.

Not as heavy aa casaiterite. Sometimes in fine hair-like inclusions. Widely distributed. With quartz, feldspar, hematite, ilmenite, chlorite, brookite, apatite.

A. Hinerals With Metallic Luster

Streak— White, gray, green, red, brown, or yellow

Name, Composition, and

Structure

Luster

Reterencea

Crystals -C Mave=M

T an pa n y

Gadolinite

Subm talU

Black

C— Priamatic, rough, rare

T an 1 nt

Greenish

M — Compact, disBemi-black

nated

Kreug, Dana, Piiraoiu

CASSriERITE, varieties

Tetragonal

BUck

Ordinary

C— Thick prismatic.

Dull

Brownish

SnO, or SnSnOj Stream ttn

knee-shaped twins,

M — Compact, reniform, botryoidal, rounded

to opaque

black

pebbles

Cubic

GARRET, varieties

Submetallic

Velvet black

Aftdradite

Brownish

tragonal trisoctaheto

opaque

black

B" -C8,Fe,Mg

drons, alone or in

R"' -Al,Fe

combination, com-

M — Granular, compact, lamellar, disseminated

; sand

Tourmalihe

Hexagonal

Submetallic

Pitch black

C— Prismatic, vertically

Pitchy

Brownish

striated, terminated

black

M' NB,K,Li,Mg,Fe

with broken or

surfaces

M— Compact, divergent columnar, dissemi-

Bluish black

nated

CORDHDUM, variety

Hexagonal

Metallic

Dark gray

Emery

M— Fine to coarse gran-

Dull

Black

AI,0, with Fe.O., Fe,0„ 810,

ular

Opaque

1. Dark Gray Or Black In Color

Hardness otot 9

Cleavage Fracture -F Tenacity

Characteristics and Aeaociates

Greenish gray C — None

F--Conchoidal, splintery Brittle

4.5 In granitic rocks and pegmatites, with fergusonite, orthite, fluorite, molybdenite.

Pale brown Pale yellow White F— Uneven

Brittle

-Prismatic, imper-

C — Dodecahed ra I ,

distinct F — Conchoidal, un

Distinguished by high specific gravity and hardness. In veins cutting granite, gneiss; also in alluvial deposits, aa stream tin. With quartz, wolframite, scheelite, arsenopyrite, molybdenite, tourmaline, fluorite, apatite.

Andradite, commonly with magnetite, epidote, feldspars, nephelite, leucite; almandile, with mica, stauTolite, andalusite, cyanite, tourmaline.

White Gray

Spherical triangular crosa-Bection and hemimorphic development important. In pegmatites; metamorphic rocks; alluvial deposits. With quartz, feldspar, cassiterite, beryl, topas, fluorite.

Yellowish C — Indistinct

brown F — Uneven

Blackish brown Brittle to tough

Corundum mixed with magnetite, hematite, quartz. Resembles iron ore, powder may be magnetic. Properties vary with composition. With mica, amphiboles, chlorite, spinel; in crystalline limestones, schists, peridotite.

A. HnTERALS WITH HETALUC LUSTER Streak — White, grayi green, red, brown, or yellow

Name, Compoeition, and References

Structure CrystalB-C Massive— M

Transparency

£IIIEL, varieties

R.&quot;Cr&quot;&#x27;0,),

R"-Mg,Fe

Gahniie

Zn,Mn

R"'-A1, Fe

Knuu, Duia, Panoiu

Cubic Submetallic Black

C— Octahedral, well de- Dull Browniab

veloped, common Nearly opaque black H — Compact, granular, Greenish

diBBeminated grains; black

Streak— Black

Hexagonal Metallic Bluieh lead

C — Tabular, rare Opaque gray

M — Disseminated grains, scales, foliated

2Ss.

GRAPHrrE (Plumbago, black Hexagonal Metallic

C MFoliated, scaly, gran- Opaque

ular, earthy

Sos

Pyrolustte

Orthorhombic ?

Metallic

Iron black

C— Often pseudo-

Dull

Dark steel gray

MnO,

morphous after manganite M— Columnar, fibrous, acicular, often divergent; dendritic;

Opaque

M7,

powdery

Pitchy

Amorphous

Black

Solid, or thick liquid

Brownish

C, H, 0, etc.

Dull

black

Ms,

Opaque

1. DARK GRAT OR BLACK Of COLOR

Hardness over 6

Cleavage — C Fracture -F Tenacity

Specific Gravity

Characteriatica and Associates

Grayiah Grayish green Pale brown White

C — Octahedral, indis-

F — ConchoidaL Brittle

CommoD. contact mineral in granu' lar limestones; in igneous rocka, especially the more basic olivinebearing types ; also rounded grains in placera. With calcite, chondrodite, serpentine, brucite, . olivine, corundum, graphite, P3Toxene8.

C — Basal, perfect Sec tile, lamellie ai flexible

Marks paper. Soft and greasy like graphite, but heavier and lighter colored. In granite with cassiterite, wolframite; also in crystalline limeatone.

Black, shiny C — Basal, perfect

Dark silver gray Sectile, lamellse ai flexible

Greasy feel; marks paper; darker than molybdenite and not a a heavy. In crystalline limestone with garnet, spinel, pyroxenes, amphiboles; also in shale, gneiss, and mica schist.

Often soils fingers. Darker than Btibnite. With psilomelane, manganite, hematite, limonite.

Characteristic odor when plastic. May be sticky. Independent deposits and impregnations in sand, shale, sandstone, limestone.

:y

A. Hdierals With Metallic Luster

Streak— Black

Ciyetallisation

Structure Luster

Crystals — C Transparency

Massive

Wad MnOj, H,0, etc.

Amorphous ? Dull Brownish

H — Elarthy, Bometimes Submetallic black

with globular struc- Opaque Black

Metallic

C — Thin, scaly, pseudo- Dull

hexagonal (tenorite) Opaque M — Earthy, sooty (melaconite)

Amorphous Pitchy

M — Compact; may show Vitreoua

strati lication; lamel- Dull

lar, rarely fibrous Opaque

Black

Brownish black

Amorphous

Submetallic

Iron black

H— Compact

Vitreoua

Black

C, principally

Opaque

3e9

Stibnite

Orthorhombic

Metallic

Dark lead gra

C— Prismatic,

bent.

Opaque

Black

twisted, c M— Fibrous,

Waded,

columnar,

granular

Orthorhombic

Metallic

Dark lead i

C — Acicular, long

Opaque

Steel gray

M— Fibrous, hair-like and felted, compact

Polybasite

Monoclinic

Metallic

Iron black

C— Tabular, six-sided.

Opaque

with beveled edges M— Compact, dissemi-

Metallic

Dark lead g

C— Tabular, thick pris-

Opaque

Iron black

Ag..Sb.

matic H — Compact, diasemi-

1. Dark Gray Or Black Hi Color

Hardness I to 3

Cleavage -C Fracture "F Tenacity

Specific

Gravity

C — Uneven F— Earthy

Crystals, brittle

F — Cubical, conchoi

F— Conchoidal, conspicuous Very brittle

C — Brachypinacoida 1,

perfect, conspicuous, jaelding long, shiny faces

Slightly Bcctile

C— Basal, rather conspicuous

F — Uneven

Brittle

spicuous F — Uneven Brittle

C — Imperfect F — Uneven Brittle

Soft varieties soil fingers. Apparently very light and floats on water, due to porosity. Usually adheres to tongue. With psilomelane, pyrolusite, s i d e r i t e , limonite.

Coatings or crusts on copper minerals, especially native copper, chalcopyrite, bornite, chrysocoUa. Earthy varieties soil fing er

Distinguished from other coals by conspicuous cubical fracture. Sometimes shows iridescence and distinct plant remains. With slate, psTite, marcasite.

Conchoidal fracture, luster, and absence of plant structure important. Often iridescent. With slate, pyrite, marcasite.

Tarnishes black, sometimes iridescent. In veins with quarts, sphalerite, galena, cinnabar, barite, gold.

Felted, fibrous masses often with feathery appearance. Heavier than Btibnite and cleavage transverse to length. Sometimes with yellow coating. With bournonite, galena, sphalerite.

Best known in crystals. Thin splinters are cherry red in transmitted light. With other silver minerals — stephanite, argentite, pyrargyrite.

More brittle than argentite. In veins with other silver minerals; also barite, galena.

:y

A. UniERALS WITH METALLIC LUSTER

Streak— Black

Refereocee

CrystalliEation Structure Crystals -C Massive -M

Luster

Color

Kmue, 48,

Duns, 2SS.

2B7

Cubic

C— Octahedral, cubical,

often distorted H — Compact, arborescent; coatings

MetaUic Opaque

Dark lead gray Black

Cubic

C—Cubea alone, or

well developed common M— Granular, cleavable aggregates, compact

Metallic Opaque

Dark lead gray

Chalcocite

Orthorhombie

agonal, deeply striated M— Granular, compact, disseminated

MetalUc Opaque

Dark lead gray, often tarnished dull black, blue, or green

Orthorhombie C— Thick tabular; cogwheel twins H— Compact, granular

Metallic Opaque

Dark steel gray Iron black

Stromeyerite

29S

Orthorhombie CTabular, rare M— Compact

Metallic Opaque

Dark lead gray

Enargite

Cu.AbS.

Orthorhombie C— Prismatic, small, rare H — Compact, granular, columnar

Submetallic

Opaque

Grayish black Iron black

Streak— Black

Tetrahedrite

Cubic

C— Tetrahedral, often

MGranular, compact

Metallic Opaque

Dark steel

gray Iron black

I. DARK ORAT OR BLACK in COLOR.

Cleavage — C Fracture -P Tenacity

Specific Gravity

Characteristics and

Dark lead gray, C— Indistinct shiny F— Hackly

Perfectly aectile

Grayish black Dark lead gray

C — Cubic, perfect,

Cuts and takes impression like lead, hence easily distinguished from other soft, black minerals. With silver, cobalt, nickel oresprouBtite, pyrargyrite, smaltite, niecolite.

Characterised by cleavage and high specific gravity. Changes to cerussite or anglesite. With sphalerite, p3vite, chalcopyrite, calcite, fluorite, barite.

2.B Dark gray, shiny C — Indistinct

3. Black, shiny F — Conchoidal

Rather brittle

Moru brittle than argentite. Often coated with malachite (green), azurite (blue). With chalcopyrite, bomite, tetrahedrite, galena.

Dark gray

C— Imperfect

Easily recognized by cross or cog-

Black

F— Uneven Brittle

wheel appearance. With galena, sphalerite, tetrahedrite, siderite.

Dark lead gray

C— Indistinct

stibnite, chalcocite.

a. 2

Resembles chalcocite but not as

Black

F— Conchoidal Slightly aectile

abundant. With copper and chalcocite, tetrahedrite.

C — Prismatic, perfect, often conspicuous F — Uneven Brittle

In artificial light usually resembles sphalerite. In veins with other copper minerals— chalcopyrite, bomite, chalcocite, tenantite, famatinite.

Dark gray Black

C — Indistinct F — Uneven Brittle

Characteristic crystals, sometimee coated with chalcopyrite. With sphalerite, galena, boumonite, siderite, malachite.

:y

A. Miherals With Metallic Luster

Streak— Black

Cryatalluation

Structure Crystals -C Massive— M

Luster Transparency

Hexagonal ' Metallic Dark gray to

C — Rare Opaque black on ex-

M — Compact, scaly, fine posure, tin

1 granular, with reni-white on

a form or botryoidal fresh frae-structure

ture

Cubic

Pitch-like -

Pitch black

C— Octahedral, rare

Submetallic

-Brownish

UO., U0„ PbO, etc.

M— Botryoidal, colum-

Du.l

black

nar, curved lamellar

Opaque

Greenish

granular, compact.

black

apparently amor

phous

Tetragonal Metallic

C— Small, rare Opaque

H — Compact, granular ' disseminated

Cubic

Metallic

Iron gray

C— Rare

Opaque

Black

Fe

M — Disseminated grains, scales, lumps

Wolframite

Monoclinic

Dark gray

C— Thick, tabular, short

Metallic

Brownish

M— Bladed, curved lamellar, granular.

Opaque

black Iron black

compact

Psilomelane

Amorphous?

Metallic

Iron black

H— Botryoidal, rem-

Dull

Bluish black

MnO„ BaO, H,0

etc.

form, etalactitic;

Opaque

Dark gray

smooth surface

Hexagonal

Metallic

Iron black

C— Thick tabular, rhom-

Submetallic

Brownish

bohedral M— Thin plates, granular, compact, disseminated grains, peb-

Opaque

black

-Sm.

bles, sand

DAS£ GRAY OR BLACK IN COLOR Hardness over 3

Cleavage C Fracture -F

Tenacity

Characteristics and

C — Basal, not conspic-

Often breaks onion-like layers. Color streaks darken on exposure. With silver, cobalt, nickel ores — proustite, smaltite, chloanthite.

3. Brownish black F — Conchoidal, 6,5 Grayish black uneven

Pitch-like appearance and fracture important. Fresh material is hard and heavy. With ores of lead, silver, bismuth; thorite, orthite, fergusonite.

C — Indistinct F — Uneven

Brittle

Often yellowish from admixture ofchalcopyrite. Withcassiterite, wolframite; in tin ore deposits.

4.B Iron gray, shiny C — Cubical, i 6. spicuous

F— Hackly

Malleable

6. Brownish black C— Clinopinacoidal, S.G Black perfect, conspicuous

F — Uneven

Brittle

Black F— Conchoidal,

Brownish black even

Brittle

Alloyed with more or less nickel. Strongly magnetic. In meteorites or basic igneous rocks (basalts). With troilite, pyrrhotite, olivine, graphite.

Structure, cleavage, and specific gravity important. Powder may be slightly magnetic. With eassiterite, quartz, mica, fluorite, apatite, scheelite, molybdenite, huebnerite.

Often with fine, sooty coating of pyrolusite. With other manganese minerals; limonite, barite.

Black C — None, partings

Brownish black may be noted

F — Conchoidal

Brittle

Sometimes slightly magnetic but not as strongly as magnetite. With hematite, magnetite, apatite, serpentine, titanite, rutile. Common in black sand.

:yG00glc

A. HnrERALS WITH UETALLIC LUSTER

Streak—

Crystallization

Name, Oompodtion, and

Structure

Luster

Crystals -C Maaeive-M

Transparency

Ilvaile

Orlhorhombie

Submetallic

Black

C — Columnar, acicular.

Opaque

Greenish

vertically striated

black

Mwk

H— Compact with radial

Brownish

Psraow

fibrous structure.

black

granular

Maghetite

Cubic

COctahedrons, dodeca-

Metallic

Iron black

hedrons, common M— Compact, granular, lamellar, diBseminated, sand

DuU Opaque

ISe. 33S.

Cubic

C— Octahedrons, alone or

Dull

Opaque

Iron black

edges often rounded H — Compact, granular.

Braunite

Tetragonal

Metallic

Black

CApparently octahe-

Greasy

Dark browndrons

, small H — Drusy crusts, granu-

Opaque

ish black

22S

lar aggregates

Orthorhombic

Submetallic

Iron black

C — Short prismatic, tab-

Greasy

Brownish

ular

DuU

black

H— Compact, disaeminated

Opaque

lao. 490,

CORDHDUM, variety

Hexagonal

Metallic

Dark gray

Emery

Always massive, fine to

DuU

Black

A1,0„ with Fe,0., Fe,0

SiO,

coarse granular

Opaque

1. DAHK GRAY OR BLACK HT COLOR Batdnu over 3

Cleavage — C Fracture — F Tenacity

Specific Gravity

5.S Black C— Finacoidal

Greenish black Brittle

Often covered with yellowish alteration product which reduces hardness. With dolomite, pyrox-

C — Indistinct, octahedral parting

F— Conchoidal, uneven

brittle

Black C — Octahedral, indie-

Brownish black tinct

F — Conchoidal

Brittle

Very strongly magnetic. Crystals usually perfect and with bright surfaces. Independent deposits; djeeeminated; black Bands. With chlorite, hornblende, pyr o:(ene, feldspar, quarti, pyrite, chalcopyrite.

Powder frequently slightly magnetic. Distinguished by associates — willemite (yellow or green), incite (red), rhodonite (flesh red), calcite.

6.6 Brownish black F — Uneven Brittle

4 . 7 Small, untwinned octahedral crys-

4.9 tals. With manganese minerals

— pyrolusite, psilomelane, hausmannite

; magnetite, barite, hema-

C — Pinaooidal, not

6.6 Brownish black Grayish black

Fracture surface sometimes iridescent. With beryl, tourmaline, spodumene, cryolite. Tantalum predominates in larUaliie and specific gravity may be as high

Black Brownish black

C — Indistinct F— Uneven Brittle to tough

Corundum mixed with magnetite, hematite, quartz. Resembles iron ore and powder may be magnetic. Properties vary with composition. With mica, am phiboles, chlorite, spinel; in crystalline limestone, schist, peridotite.

UniERALS WITH METALLIC LUSTER Streak— Metallic wbite or steel gray

CryBtallizatioi Structure Crystals Massive — M

Transparency

Cubic, at— 39° C, liquid Metallic at ordinary tempera- Opaque

Sylvanite

C— Rare

M— Branching arborescent forms, simulating written characters; bladed, columnar, granular

MetalUc Opaque

Silver white Steel gray, at times with brassy tinge

Bismuth

Bi

Hexagonal C— Rare

M— Reticulated, arborescent, platy

Metallic Opaque

Silver white, with reddish tinge

Silver

Ag

Cubic

C— Small, often distorted M— Grains, scales, plates, twisted hair-or wirelike forms, lumps

Metallic

Opaque

Silver white, tarnishing yellow, brown, or black

gray

Cubic C— Rare

M— Plates, coatings, embedded grains

Metallic Opaque

Silver white

Antimony

Sb

Hexagonal C— Rare

M — Compact, granular, lamellar

Metallic

Opaque

Tin white

Light steel gray

Djwcrasite

Ortho rhombic

C— Columnar, tabular,

M — Compact, granular, nodular, coatings

Metallic Opaque

Silver white, tarnishes yellow or black

2. Metallic White Or Light Bietallic Gray Ht Color.

Hardneas 1 to 3

Cleavage — C Fracture -F

Tenacity

C — Clinopinacoidal , perfect, usuallij' conspicuous

F — Uneven

Brittle

ResembleB ancient script, hence graphic tellurijim. With gold, cakverite, aphaierite, pyrite, tetrahedrite.

2. Lead gray, shiny C — Basal, perfect, usu- 3.6 ally conspicuous

Sectile

2.S Silver white, C — None

3. shiny F — Hackly Light lead gray, Malleable, ductile

Often shows brassy tarnish colors. With silver, cobalt, nickel, tin ores — smaltite, niccolite, chloanthite, cassitrit; wolframite.

Color and streak darken on exposure. With silver, lead, araenic, cobalt, nickel ores — argentite, pyrargyrite, proustite, smaltite, galena; fluorite, calcite, barite.

Hardness over 3

C— None 13.7

F— Conohoidal 14,1

Brittle to malleable

With native mercury, cinnabar, and silver minerals.

Tin white Lead gray

C — Basal, perfect, usu

ally conspicuous F— Uneven

Brittle

C— Domatic F — Uneven Sectile

Does not tarnish readily. With silver, arsenic, and other antimony minerals — kermeaite, stibnite, smaltite, allemontite. Sometimes coated with white oxide of antimony.

A. milERALS WITH METALUC LUSTER

Streak— Hetallic white o

r steel gray

Name, Compoaitioii References

,aiid

CrystaUization Structure Crystaia -C MaBBive=M

LuBter Transparency

Color

Platinum

Cubic

C— Small, rare

Metallic

Opaque

Tin white

Steel gray

Iridoshium

Hexagonal

Metallic

Tin white

CThin tabular

Opaque

Light steel

M— Scales, flattened

gray

p-ains

Streak— Black

Blolybdenite MoS,

Hexagonal

C— Tabular, rare H— Disseminated grains, scales, foliated

Opaque

Bluish lead gray

B18Mutkinitb

Orthorhombic

C — Acicular, rare M— Granular, foliated, fibrous

Metallic

Opaque

Lead gray Tin white

Stibhtte

Orthorhombic

C— Prismatic, bent, twisted, common

M— Fibrous, bladed, columnar, granular, compact

Metallic

Light lead gray

Jambsonitb

Orthorhombic

C — Long, acicular M— Fibrous, hair-like, felted, compact

Metallic

Opaque

Steel gray Lead gray

Cubic

C— Cubes, alone or with

octahedron, common,

well developed M— Granular, cleavable

Metallic Opaque

Lead gray

aggregates

Hetaujc White Or Light Metallic Gray Ih Color. 43

HardneBS more than 3

Cleavage —C Fracture

Tenacity

I Specific

Light Bteel gray, C — None shiny F — Hackly

Malleable, ductile

C — Baaal, perfect F — Uneven Slightly malleable

Heavier than silver and does not tamiah. May be magnetic if much iron be present. With chromite, magnetite, gold, iridoanuum.

Distinguished from platim greater hardness. In place with platinum, gold, chromite

by

Hardness 1 to 3

Dark lead gray, C— Basal, perfect greenish on SecUle, lamelte fle:(ible glazed porcelain (graphite, shiny black)

C — Brachypinacoidal, perfect, rather conspicuous

Slightly sectile

C — Brachypinacoidal, perfect, conspicuous, yielding long shiny faces

Slightly sectile

Marks paper. Soft and greasy like graphite but heavier and lighter colored. In granite with cassitente, wolframite; in crystalline limestone. Heavier and lighter in color than stibnite. With cassiterite, bismuth, chalcopyrite, gersdorffite, wolframite- Differs from galena in cleavage and specific gravity. TamiaheH black, sometimes iridescent. In veins with quartz, sphalerite, galena, cinnabar, barite, gold.

Grayish black CBasal, rather conspicuous F — Uneven Brittle

Dark lead gray C — Cubic, perfect, very Grayish black conspicuous

Brittle

Felted fibrous masses, often with feathery appearance. Heavier than stibnite and cleavage transverse. With bournonite, galena, sphalerite.

Characterized by excellent cleavage and high specific gravity. Changes to cenissite or anglesite. With sphalerite, pyrite, chalcopyrite, calcite, fluorite, barite.

A. MnrERALS WITH METALLIC LUSTER

Streak— Black

Name, Compoaition, and

References

Cryetallization Structure CryatalBC MaBsive-M

Luster Transparency

Color

Arsenic

As

KraiH, Dmui

uul

Hexagonal

C— Rare

H — Compact, scaly, fine

grained, renitorm,

iwtryoidal

Metallic

Opaque

Metallic Opaque

Tin white, on

ture

Dombtkite

Cu.As

C— Unknown H— Compact, reniform, botryoidal

Tin white, with yellow and

variegated tarnish

L5Llinoite

21S

Orthorhombic C— Rare

H — Granular, disseminated, compact

Metallic

Opaque

Silver white Steel gray

Llnnodte

Cubic

C— Octahedral

MGranular, compact

Metallic Opaque

Steel gray, at times with reddish tinge

Cobaltite

Cubic

C — Cubes, pyritohedrona, small, well developed MGranular, compact

MetaUic Opaque

Silver white Steel gray, at

times with

reddish

tinge

Snultlte

Cubic C— Rare

H — Granular, compact

Metallic Opaque

Tin white

Light steel

gray

Metallic Opaque

Cblouitliite NiAe,

Cubic

C— Rare .

M — Granular, compact

Tin white

Light steel

gray

2. Metallic White Or Light Bietallic Gray Iit Color

Hardness

Hard-

Streak

Cleavage -C Fracture -F

Tenacity

Specific Gravity

. Characteristics and

Associates

Lead gray Grayiah black

Grayish black

C— BaBaL,Tiot conapicu

F— Uneven, granular Brittle

Often breaks in concentric or

darken on exposure. With ailver, cobalt, nickel orea—

proustite, smaltite, chloanthite.

S.6

C— None F— Uneven

Tamishes readily and then resembles chalcopyrite, but much heavier. With native copper, silver; niccolite, whitneyite.

Grayish black

C — Basal, not conspic-

Tarnishes gray.

1 arsenopyrite.

Frequently in serpentine. With siderite, cassitrite, arsenopyrite, hornblende.

6.6 Grayish black ' C — Indial

Tarnishes copper red. With chalcopyrite, pyrrhotite, siderite; cobalt and nickel minerals.

C — Cubic, not conspic-

May show red tarnish. Often with pink coating of erythrite (cobalt bloom). With native silver, smaltite, niccolite, pyrrhotite, chalcopjTite.

S.6 Grayish black

C Indistinct F — Uneven Brittle

May have dull tarnish and pink coating of erythrite. With niccolite, cobalt! t, native bismuth and silver, proustite, barite, fluorite, calcite.

Tarnishes dull and often coated with green annabergite (nickel bloom). Resembles smaltite but not as abundant. With niccolite, cobaltite, proustite, native silver and bismuth, calcite.

A. hhierals with metallic luster

Streak— BUck

CryEtallJzation Structure Crystals -C Massive— M

Luster Transparency

Arsehopyrite

Kreus, Dana,

Orthorhombie

Metallic

Tin white

C— Prismatic, common M — Compact, granular, Mo9 columnar, radial

Opaque

Light steel gray, tarniahes yellow

Metallic

Steel gray

C— Tabular, often

twinned, resernbling cock's combs

Opaque

Pale brass yellow, more brassy on ex-

H — Compact, atalactitic, 212 globular, radiated

posure

3. Ketallic White Or Light Metallic Gray Ih Color 47

Hardness more than 3

Cleavage Fracture -F

Tenacity

Gravity j

B.S

Dark grayish

C— Prismatic, not con

Whiter than marcasit. More

black

spicuous F — Uneven Brittle

common than amaltite or cbloanthite. With ohalcopyrite, pyrite, sphalerite, cassiterite, amaltite, native gold and silver, serpentine

Dark greenish

C— IndiBtinct

Alters to limonite, melantrite.

black

F— Uneven

Brittle

With other sulphides— galena, sphalerite, chalcopyrite, pyrite;

A. Miherals With Metallic Ldster

Streak — Gray, brown, or yellow

Ciystallization Structvire

Crystals — C

Luster Transparency

LIHOHITE, varieties

— Earthy, porous, clay-like

Earthy

DuH

Opaque

Yellow

Brownish yellow

KrauB, Dana, Psrat

Monoclinic C— Rare H — Compact

Metallic Opaque

C— SmaU,

HGrains, scales, nuggets, dust

Metallic Opaque

Golden yeHoi Brassy yelloi Light yellow

Sphalerite

Cubic

C— Tetrahedral,

H — Compact, fine or coarse grained, cleavable aggregates

Adamantine Transparent to

Hexagonal

C — Hemimorphic, rare M— Compact, granular foliated

Vitreous Translucent t opaque

Oraie yelloi Reddish yel-

UncomaioB Mior.

Tetragonal Resinous Orange yellow

C — Square prisms with Vitreous Brownish yelbipyramids

Transparent to low M—Compact, dissemitranslucent

:y

HardneBs 1 to 6

Cleavage — C Fracture — F

Tenacity ,

Specific Gravity

Yellowish

C— None

brown

F— Earthy

Brittle

Yellow ochcT, earthy, may have greasy feel, when impure gritty; bog iron ore, porous.

C— None F — Uneven

Brittle

With gold, eylvanite, petzite, tetrahedrite, pyrite.

C — None F— Hackly Malleable, ductile

Does not tarnish. Differs from other soft, yellow minerals in atreak, specific gravity, and tenacity. Frequently in quarts veins, placers. With pyrite, galena, sphalerite, areenopyrite, stibnite, chalcopyrite.

i. Orange yellow 4.B Reddish yeUo?

— Dodecahedral, perfect, conspicu-

— Basal, perfect, usually conspicu-

Color and streak vary with impurities. Extensively in limestone. With galena, chalcopyrite, pyrite, barite, fluorite, siderite, rhodochrosite.

Distinguished by associates — calcite, franklinite (black), willemite (yellow to green), rhodonite (flesh red}. On exposure becomes coated with the white carbonate.

C — Prismatic, n

conspicuous F — Conchoidal Brittle

Yellow orangite is sometimes surrounded by dark brown to black thorite; latter is thought to be decomposed orangite.

:y

A. HmERALS WITH METALLIC LUSTER

Streak— Gray, brown, or yellow

Crystalliiatioi Structure Crystals Massive — U

Transparency

Orthorhombic Submetallic YeHow

C — Small, thin tabular, Translucent to Brownish yel- PeO . OH needle-like ; paralopaque low

leliy grouped or in Mixea scaly, fibrous vel'

Knaa, Dana, raaa vety crusts

Streak— Black

Domeykiti

Cu,As

Hexagonal Metallic

C — Needle-like, radiat- Opaque

ing groups, hair tufts H — Fibrous, compact

CUnknown Metallic

M' — Compact, reniform, Opaque botryoidal

Brass yellow Bronze yelloi

Yellow and variegated

colors on exposure

Chalcopyrite

Tetragonal

Metallic

Opaque

bling tetrahedrons.

M— Compact

Pentlandite

Cubic

Metallio

C— Rare

Opaque

K — Compact, granular

Orthorhombic

C— Tabular, often

FeS,

cock's combs M— Compact, stalactitic, globular, radiated

Brass yellow Golden yelloi

:y

Hard-nesa

Streak

Cleavage -C Fracture -F Tenacity

Specific Gravity

CharacteriBticB and Associates

6.B

Yellow YeUowish

brown

C— Brachypinacoidal, 4 .

perfect 4.4 F — Uneven, splintery Brittle

Usually with other iron ores; in cavities with hematite or limonite.

Dark greenish black

C— Basal

F-Uneven Brittle

Often in cavities in Umeatone or hematite. With pyrrhotite, chalcopyrite, chloanthite, barite, fluorite.

F — Uneven Brittle

When tarnished resembles chalcopyrite, but much heavier. Tin white on fresh fracture. With native copper and silver, niccolite, whitneyite. MohawkUe nickeliferous variety.

Greenish black

C— Indistinct F— Uneven Brittle

3.B

Black

C— Octahedral, often

F— Uneven

Brittle

e.

Dark greenish

black Brownish black

C— Indistinct F — Uneven

Brittle

Softer, and deeper yellow in color than pyrite. Frequently with iridescent tarnish. With pyrite, bomite, galena, sphalerite, tetrahedrite, chalcocite.

Non-magnetic. With chalcopyrite, pyrrhotite.

Distinguished from pyrite by crystallization and lighter color on fresh fracture. Alters more readily than pyrite, forming limonite, melanterite. Occurrence same as for pyrite, but not as abundant.

A. Hiberals With Metallic Luster

Streak — Black

Name, CompOBition, and References

Crystallization Structure Crystals Massive — M

Luater Transparency

PYRITE (Iron pyrites, fool'H Cubic Metallic Brass yellow

gold) C — Cubes, octahedrons. Opaque Golden yellow

FeS, pyritohedrons, very with varie-common

, often stri-gated tar-ated

nish

Mo8 H — Compact, fine gran- Kraiu. DttDfl, Pareoni ular; botryoidal, stal-

:y

Cleavage — C

Fracture Tenacity

Chamcteriatics and

GreeniBh black C — Indistinct Brownish black F— Uneven Brittle

Harder than chalcopyrite. Alters to limonite, copiapite. Widely distributed in all types of rocks. With other sulphides — galena, sphalerite, chalcopyrite.

:y

A. UHEIULS WITH METALLIC LUSTER Streak—Oray, red, or ;llow

Crystallisatioi Structure CrysUlfl-C Haesive— H

Luater Transparencjr

Hex&goal Metallic

C — Rare Opaque

H — Reticulated, arbo- Uoeea rescent, platy

Calaverite AuTe,

3oa

C— Rare H-Compact

MetalUc Opaque

Light bronze yellow

COPPER Cu

ZJi.

Cubic

C— Cubes, octahedrons, - tetrabexabedrons

M— Scales, plates, lumps, arborescent aggregates

Metallic Opaque

Copper red,

readily red, blue, green, black

Gold

2S4

Cubic

C— Small, distorted, rare M— Grains, scales, dust, DUggets

Metallic Opaque

Golden yellow Brassy yellow Light yeUow

Streak— Black

Cubic

C— Rare

H — Compact, granular

BORHITE Cu,FeS,

5S.

Metallic Opaque

Bronze brown Copper red, on treat fracture

HUlerite NiS

Hexagonal

C— Needle-like, often in

radial groups, hairtufta

H— Fibrous, compact

Brass yellow Bronie yellow

Douetkite

Cu,Aa

C— Unknown

M— Compact, reniform, botryoidal

Metallic Opaque

Yellow

Variegated, on exposure

4. Brass, Bronze, Or Copper Red Ih Color

Hard-

Streak

Cleavage -C Fracture -F Tenacity

Specific Gravity

Characteristics and

Associates

Lead gray, shiny

C— Baaal, perfect, ubl ally conspicuous

Sectile

Often shows braBsy tarnish. Frequently with silver, cobalt,

lite, chloanthite, cassiterite; wolframite.

Gray

C-None

F— Uneven Brittle

With gold, sylvanite, petzite tetrahedrite, pyrite.

Copper red,

Shiny

C— None F— Hackly Ductile, malleable

Cementing material in conglomerate or aiming cavities in trap. With cuprite, malachite, azurite, native silver, tenorite, epidote, prehnite, datolite, leolites, quarti, calcite.

Golden yeUow

C-None F— Hackly Malleable, ductile

Does not tamish. Differs from other soft yellow minerals in streak, specific gravity, and tenacity

. Frequently in quartz veins; placers. With pyrit, galena, sphalerite, arsenopyrite, stibnite, chalcopyrite.

over 3

Grayish black

F— Uneven Brittle

Usually with peacock tarnish

malachit, cassiterite, siderite.

Dark greenish black

C— Basal F— Uneven Brittle

In cavities in limestones, hematite, dolomite. With pyrrhotite, chalcopyrite, chloanthite, barite, fluorite.

C — None F — Uneven Brittle

When tarnished resembles chalcopyrite but much heavier. Tin white on fresh fracture. With native copper, silver; mccoUt, whitneyite. Mohawkite, niekeliferous variety.

A. mnERALS WITH METALLIC LUSTER

Streak— Black

Structure Crystals -C Massive -M

Name, Composition

I Luster

Color

chalcopyrite;

Tetragonal

bling tetrahedrons,

MetalUc Opaque

Brass yellow Goldea yellow

Faooa — Compact, granular

Pentlandite

Cubic

C— Extremely rare

H— Compact, granular

Metallic Opaque

Light bronze yellow

Pyrrhotite

Hexagonal

C— Tabular, rare

H — Compact, granular

Metallic Opaque

Hexagonal C— Rare

M — Compact, dissemi-

Metallic Opaque

Orthorhombic

C Tabular, often

twinned resembling

cock's combs H — Compact, stalactitic,

globular, radiated

Metallic Opaque

Steel gray Pale brass yelbrassyoi

C — Cubes, octahedrons, pyritohedrons, very common, often stri-

H — Compact, line granular; botryoidal, stalactitic

Metallic

Brass yellow Golden yellow, with variegated tarnish

:y

4. Brass, Bronze, Or Copper Red Iii Color

Cleavage — C Fracture -F Tenacity

3.S GreeniBh black

C — Indistinct F — Uneven Brittle

Softer, and deeper yellow in color than pyrit. Frequently with iridescent tamiah. With pyrite, bomite, galena, sphalerite, tetrahedrite, chalcocite.

3.B

Black

C— Octahedral, often

Non-magnetic. With

Chalcoconepicuou

B P-Uneven Brittle

pyrite, pyrrhotite.

C — Basal, not conapic- 4.5 Powder frequently attracted

uous 4,6 by magnet. Subject to dark

P — Uneven brown tamieh. In basic igneoufl

Brittle rocks. With chalcopyrite, pyrite,

pentlandite, galena.

Dark brownish C — Indistinct black F— Uneven

Brittle

Often with green coating of annabergite (nickel bloom). With cobalt, nickel, silver minerals — smaltite, prouatite, chloanthite, native silver; native bismuth and

Dark greenish C — Indistinct black F — Uneven

Brittle

Greenish black C — Indistinct Brownish black P— Uneven Brittle

Distiaguished from pyrite by orystalliKBtion and lighter color on fresh fracture. Alters more readily than pyrite, forming limonite, melanterite. Occurrence same as for pyrite, but not as abundant.

Alters to limonite, copiapite. Widely distributed in all of rocks. With other sulphides — galena, sphalerite, chalcopyrite.

A. MinERALS WITH METALLIC LUSTER

Streak— White, gray, green, red, brown,

Name, Composition, and References

Crystallisation Structure Crystals -C Massive— M

Luater Transparency

Amorphous T Dull Brown

H — Earthy, aometimee SubmetafUc Blackish

MnO„ H,0, etc.

with globular struc-

Opaque

brown

Erwu, Domi, Fanom

ture

LIMOHITE, varietiea

C— Unknown

Dull

Yellowish

M— Compact, earthy, porous, pisolitic, ooUtic

Earthy Opaque

brown Dark brown

iron*tone

Sb, 350. 221

HEMATITE, varieties

Hexagonal

Dull

Brownish

Red other Pe,0, Oolilic

M— Fine granular, earthy, scaly, oolitic, tossiliferouB

Earthy Opaque

Cherry red

Hexagonal Adamantine Scarlet red

C — Rhombohedral, thick Dull Brownish red

tabular, small, rare Transparent to

M — Fine granular, fi-opaque

brous, diesemihated,

earthy coating

Hexagonal

Adamantine

Scarlet

C — Small, complex, rare

DuU

Vermilion

Ag.AsS,

bands

Transparent to translucent

Pyrargyrite

Hexagonal

Admantine

Dark red

C-mall, complex, rare

M — Disseminated, crusts.

Transparent to

Sb. 311.

opaque

Copper

Cubic

Metallic

Copper red,

C— Cubes, octahedrons.

Opaque

tarnishing

tetrabexahedrons

readily to

Cu

H— Scales, plates, lumps, arborescent aggre- 282 gates

red, blue, gteen, black

5. RED, BROW, OR BLUE IH COLOR Hardnesa 1 to 3

Cleavage — C Fracture — F Tenacity

C— None

F— Earthy BritUe

C — None

F— Earthy Brittle

Very soft varieticB soil fingers. Apparently very light and floats on water, due to porosity. Usually adheres to tongue. With psilomelane, pyroluute, aiderite, limonite.

Brovm ocher, earthy, may soil fingers; bog iron ore, porous; brown clay irontlone, massive or concretionary, impure from clsy.

Cherry red C— None

Reddish brown F— Earthy Brittle

Red ocher, earthy; oolitic, 1

; fossUiferous, replace' t of Belle.

Scarlet Reddish brown

C— Prismatic, not

FUneven Brittle to sectile

Color, streak, high specific gravity important; the latter often reduced by gangue. Disseminated

in aihcious rocks, with native

gar, stibnite.

2.5 Cherry red 3. Purplish red

Copper red,

C— Indistinct F — Conchoidal Brittle

C — Indistinct F — Conchoidal Brittle

C— None F— Hackly

Ductile, malleable

Termed light ruby silver ore. Distinguished from cinnabar by associates. With pyrargyrite, in veins with other silver minerals

galena.

Frequently as gray or dark, red bands, dark ruby silver ore. With proustite, in veins with other silver minerals and galena.

Cementing material in conglomerate, or filling cavities in trap. With cuprite, malachite, azurite, native silver, tenorite, epidote, prehnite,datolite, zeolites, quarts, calcite.

A. Miherals With Metallic Luster

Streak— White, gnj, green, red, brown, or yellow

Name, Composition, and References

CrystalliEation Structure Crystals -C Massive— H

Luster Transparency

LIHOniTE, varieties

Compact Fe.O,(0H), Bog iron or. Broum clay ironatOTie

C — -Always pseudo- , Metallic morphs, commonly Dull after pyrite, marea- Opaque site, siderite M — Compact, stalaetitic, botryoidal, nodular; Uoan often with internal

Kram, Dana, Panons radial fibrous struc-

Cubic Submetallic

C— Octahedral, rare Dull

H — Botryoidal, colum* Opaque nar, curved lamellar, granular, compact; apparently amorphous

Yellowish

brown

Dark brown

Blackish brown

HEMATITE, varieties

Fe,0, Compact

Hexagonal Submetallic Brownish red

M — Compact, granular, Dull Dark red

columnar, splintery. Opaque Blackish red

radiated, reniform

and tiotryoidal

Cubic Submetallic Brown

C — Tetrahedral, common Resinous Yellowish

M — Cleavable, fine and Opaque to brown

coarse grained aggretranslucent Reddish

gates, compact brown

CUPBTTE Cu.O

Cubic Adamantine

C — Octahedrons, dodec- Dull

ahedrons, alone or Translucent t( in combination, com-opaque

H — Compact, granular, earthy; slender crystal aggregates (- cotrichiU)

6. RED, BROWIT, OR BLUE DT COLOR Hardness 3 to 6

Cleavage — C Fracture — F Tenacity

Yellomsh

F— Conchoidal,

brown

even, earthy

Brittle

Often with black, vamish-like

surface, passing into soft, yellow ocherouB variety. Compact limoft- Ue, maasive, with fibrous structure, rather pure; brovm clay ironaUme massive or concretionary, impure from clay, sand; bog iron ore, porous.

Dark brown F— Conchoidal,

E 1 Olive green even

Grayish Brittle

Structure and fracture important. Fresh material is hard and heavy. With ores of lead, silver, bismuth; also orthite, thorite, fergusonite.

Cherry red Reddish brown

C — None, parting

F — Uneven, splintery BritUe

Light brown Pale yellow

C— Dodecahedral, perfect, conapicu-

Brittle

Brownish red Dirty brown

C— Indistinct F— Uneven Brittle

ATgillaceous hemaliU, impure from clay, sand, jasper; compact hematite, usually quite pure.

Color and streak vary with impurities. Extensively in limestone. With galena, chalcopyrite, pyrite, barite, fluorite, siderite, rhodochrosite.

Characterized by associates, usually with copper minerals — malachite (green), azurite (blue), chalcocite and tenorite (black), chalcopyrite ( yellow ), native copper.

D.gizjcCyGoOgle

A. HOfERALS WITH METALLIC LUSTER

Streak — White, gray, green, red, brown, or yellow

CryBtalliEatioi Structure Crystals -C Maasive'M

Luster Transparency

Hexagonal Subadaman- Dark red C — Hemimorphic, rare tine Blood red

H — Compact, granular, Vitreous

' foliated Translucent to

A opaque

Goethite FeO.OH

Huebnerite MnWO,

Wolframite

Orthorbombtc Submetallic Reddish brown

C — Small, thin, tabular, Translucent to Dark brown

needle-like; pa ra 1-opaque Red

belly grouped or in

scaly fibrous velvety

crusts H — Reniform, Btalactitic

Honoclinic Submetallic Reddish brown

C — Long, fibrous, bladed, Resinous Brown

stalky, often diver- Opaque to

gent, without good translucent

terminations M— Compact, lamellar,

granular

Monocliuic Submetallic Reddish brown

C — Thick, tabular, short Opaque Dark brown

columnar, often large M — Bladed, curved lamellar, granular, compact

Monodinic

C— Tabular, rare

H — Compact, granula

bladed, diesem

nated grains

Submetallic Dark brown

Resinous Blackish Opaque to brown

translucent Grayish brown

Tetragonal

C Pyramidal, tabular, rarely prismatic

Reddish brown Yellowish brown Blackish brow D

:y

S. KED, BROWV, OR BLUE m COLOR

HaidnesB 3 to

Cleavage . Fracture -F Tenacity

Specific

Gravity

CharacteriaticH and . Associates

Reddish yellow Orange yellow

C— Basal, perfect, usually conspicu-

F-Uneven Brittle

4.B

Yellow Yellowish brown

C — Brachypinacoidal,

perfect F — Uneven, aplintory Brittle

4.B

Yellowish brown Greenish gray

C— Clinopinacoidal, perfect, conapicu-

Diatinguiahed by asaociatea — calotte, franklinite (black), willemite (yellow to green), rhodonite {flesh red). On exposure becomes coated with the white carbonate.

Usually with other iron ores; in cavities in hematite or Lmonite. Crystals and cleavage distinguish it from limonite.

Structure, cleavage, specific gravity important. In quarts veins. With fluorite, pyrite, soheelite, wolframite, galena, tetrahedrite.

G.B

Dark red brown

perfect, conspicu-

F— Uneven Brittle

Grayish Brownish gray Pale brown

C— Pinacoidal, indistinct

F— Uneven ,conohoidal

Brittle

B.6

Gray White

C— Pyramidal, basal,

perfect F-Sub-conchoidal Brittle

Distinguiahed from huebnerite by streak. Powder may be slightly magnetic. With cassiterite, quartz, mica, fluorite, apatite, scheelite, molybdenite, buebner-

Often coated with yellowish or brownish alteration product. Disaeminated in the more acid igneoua rocks; Umestone. With magnetite, epidote, quartz, f eld- Crystals often resemble elongated octaliedrons. With br o ok i t e, Tutile, ilmenite, adularta, titanite, gold.

:y

A. HDfBKALS WITH METALLIC LUSTER

Streak— White, gray, green, red, brows, or yellow

Name, Composition, and

Structure

Luster

Crystala-C

Transparency

Massive -M

BrooWte Orthorhombic

Metallic

Blackish

brown

TiO, with hexagonal

Opaque to

Blackish

red

7fl, 347, 252

Perovsldte CaTiO,

Pseudocubic

C— Apparently cubes, highly modified, often striated

H — Reniform aggregates, rounded grains

Metallic Reddish brown

Adamantine Blackish

Opaque to brown transparent

Streak — White, gray, green, red, brown, or yellow

Gadolinite

Monoclinic

C — Prismatic, rough.

Submetallic Translucent t

opaque

Rdtile

TiOj or TiTiO.

Tetragonal Metallic

C — Prismatic, vertically Adamantine

striated; twinned. Opaque to

yielding knee-shaped transparent or rosette forms H — Compact, dissemi-

CASSITERITE, varieties

Tetragonal

Adamantine

Reddish brown

Ordinary

C— Thick prismatic.

Resinous

Yellowish

SnO, or SnSnO, Wood tin.

knee-shaped twins.

Dull

brown

Stream tin

common

Translucent to

Dark brown

M— Compact; reniform,

opaque

botryoidal, rounded

pebbles, often with internal, radial fibrous structure, wood

:y

S. Red, Browit, Or Blue Dt Color

6.6 Pale yellowish C — Indistinct

Gray Brittle

Crystals may be striated; not twinned like rutile. With rutile, anatase, titanite, adularia, neph-

White

Grayisli

C— Cubical, fairly 4,

distinct 4 . 1 F — Uneven Brittle

With chlorite, magnetite, serpen-

Hardness over 6

C— None 4 , F— Conchoidal, splin- 4.5

tery Brittle

C— Prismatic, pyram- 4.2 idal, not con- 4.3 spicuous

F— Uneven

Brittle

Greenish gray

In granitic rocka and pegmatites. With tergueonite, orthite, fluorite, molybdenite.

Pale yeUowish

brown Gray

Not as heavy aa oassiterite. Often in fine, hair-like inclusions.

quartz, felspar, iimenite, chlorite, brookite, apatite.

Pale yellow CIndistinct

Pale brown F — Uneven

White Brittle

Distinguished by high specific gravity. In veins cuttinggranite, gneiss; in alluvial deposits, as stream (in. With quarti, wolframite, scheelite, arsenopyrite, molybdenite, tourmaline, fluorite, apatite.

:y

imiERALS WITH METALLIC LUSTER

Streak— Black

Name, Composition, and

Structure

Luster

Color

References

Cryatala-C Massive -M

Transparency

W*D

.Amorphous 7

Dull

Brown

M— Earthy, sometimeB

Blackish

MnO, H,0, etc.

Moses and

with globular structure

Opaque

brown

Kraus, Dana.

Hexagonal

Submetallic

Indigo blue

C— Tabular, rare

Resinoua

Blackish blue

CuS

H — Compact, granular,

Opaque

Cubic

Metallic

Bronze brown

C— Rare

Opaque

Copper red .

Cu,FeS,

M— Compact granular

tarnishes

readily

Cubic

Brown

C— Octahedral, rare

Dull

Blackish

U0„ U0„ PbO, etc.

M— Botryoidal, columnar, curved lamellar, granular compact, apparently amor-

Opaque

brown

phous

Pyrrhotite

Hexagonal

Bronze brown

C— Tabular, rare

Opaque

Bronze yellow

FeS

M— Compact, granular

Se. 206,

Wolframite

Monoclinic

Grayish brown

C— Thick tabular, short

Opaque

Dark brown

columnar, often large M— Bladed, curved lam-cellar

, granular

Hiccolite

Hexagonal

Metallic

Light copper

C— Rare

Opaque

red

M— Compact, disseminated

6. RED, BROWIT, OR BLUE IH COLOR HardocM 1 to 6

Cieavage — C Fracture — F Tenacity

Dark gray Black

C— Basal, perfect

F — Uneven

Flexible in thin plates

Grayish black

C — Indistinct F— Uneven Brittle

Brownish black Grayish black

F— Conchoidal, un- Brittle

Very soft varieties soil fingers. App fly very light and floats w t due to porosity. Usu- Uy dh es to tongue. With p 1 m 1 n , siderite, pyrolusite, Im t

f 1 y haracteristic;bornite,

blue only on surface. With chalcopyrite, bornite, chalcocite.

Usually with peacock tarnish colors — purple copper ore. With chalcopyrite, chalcocite, malachite, casaiterite, siderite.

Structure and fracture important. Fresh material is hard and heavy. With ores of lead, silver, bismuth; also thorite, orthite, fergusonite.

Dark grayish

C— Basal,

black

spicuous F— Uneven Brittle

Brownish black perfect, conspicu-

6.6 Dark brownish C — Indistinct black F — Uneven

Brittle

Powder frequently attracted by magnet. Subject to dark brown tarnish. In basic igneous rocks. With chalcopsrite, pyrite, pentla nite, galena.

Structure, cleavage, specific gravity important. Powder may be slightly magnetic. With cassiterite quartz mica, fluorite, apatite scheelite molybdenite,

Often with green crust of annaberte {nickel bloom). With cobalt nickel silver minerals — smaltite proustite pyrargyrite, chloanthite native bismuth and arsenic calcite

:y

MinERALS WITH ROR-METALLIC LUSTER

StieRk — Gieen, red, brown, yellow,

or bluk

Crystalliifltion

Structure

Luster

Color

References

Cryataifl-C Massive -M

Transparency

Never in crystals

Waxy

Black

M— Compact, fibrOuB,

Submetalhc

Brownish

C„H„+.

lamellar

Translucent

black

md*

Kraiu, Dana, Panoot

Hexagonal

Dull

Dark gray

C— Tabular, rare

Opaque

Iron Mack

MScaly, foliated, granular, earthy, sooty

Mblaconite

Dull

Iron black

M — Earthy, sooty

Opaque

Dark gray

CuO

Sb, 332. 28B

Pitchy

Amorphous

Black

Solid, or thick liquid

Brownish

C, H, 0, etc.

DuU Opaque

black

2S9. 545. 3tM

Wad

Amorphous 7

Dull

M— Earthy, sometimes

Submetallic

black

MnO,. H,0, etc.

with globular structure

Opaque

Black

Amorphous

Dull

Black

M— Compact, fibrous.

Opaque

C, H, 0, etc.

commonly with

black

woody structure

Pitchy

Black

H — Compact, may show

Vitreous

C, H, 0, etc.

stratification; lamel-

DuU

black

lar, fibrous

Opaque

2B2. 5*8. 3fl6

Amorphous

Vitreous

Iron black

M— Compact

Black

C, principally

Opaque

1. DABK GRAY OR BLACK m COLOR

Hardness 1 to 3

Hardness

Streak

Cleavage -C Fracture -F Tenacity

Specific Gravity

Characteriatica and

C — None, apparently amorphous

Plastic between fingers ; may be sticky

Easily indented by finger nail.

fee!. In sandstonea and ahales; with petroleum and coal.

Dark gray Iron black

C— Basal, perfect

Greasy feel. Marks paper. Often impure. In crystalline limestone with garnet, spinel, pyroxenes, amphibolea; also in shale, gneiss, mica schist.

2.S

Black

F— Earthy

Coating on copper minerals, especially native copper, chaloopyrite, bornite, chrysocolla. Soils

fingers.

J.

C— None

F— Conchoidal, conspicuous Brittle to flexible

Characteristic bituminous odor when plastic, and then sticky. Independent deposits and im-sandstones

, limestones.

Dark brown Brownish black Black

F— Earthy Brittle

Very soft varieties soil fingers. Apparently very Ught and floats on water, due to porosity. Usually adheres to tongue. With psilomelane, siderite, pyrolusite, limonite.

2.G Blackish brown Brittle to tough

less carbonized plant May disintegrate on

exposure. Jet, compact, coal black variety with resinous luster.

2. Black F — Cubical, conchoid-

Brittle

F — Conchoidal, conspicuous Very brittle

Distinguished from other coals by conspicuous cubical fracture. Sometimes shows iridescence, or distinct plant remains. With slate, pyrite, marcasite.

Conchoidal fracture, luster, and absence of plant structure important. Often iridescent. With slate, pyrite, marcasite.

B. WnERALS WITH NOIT-HETALUC LUSTER

or black

Crystallization

Name, Composition, and

Structure

Luster

Crystals -C Massive -M

Transparency

*AUcamite

Orthorhombic

Vitreous

Greenish black

C— Slender prismatic,

Adamantine

usually in confused

Transparent

aggregates

to nearly

H — Fibrous, granular.

opaque

Kmu8. Dana, Panioiu

compact, crusts,

sand

Cubic

Pitch-Uke

Pitch black

C— Octahedral, rare

Submetallic

Brownish

U0„ UOa, PbO, etc.

H — Bottyoidal, colum-

Dull

black

nar, curved lamel-

Opaque

Greenish

lar, granular, com-black

pact, apparently

amorphous

Siderite

Hexagonal

Vitreous

Brownish

C— Rhombohedral,

Dull

black

curved or saddle-

Black

shaped, common

to opaque

M— Cleavable, granular.

compact, botryoidal

lis. 359, 223

Cubic

Black

C— Tetrahedral, common

Resinous

Yellowish

ZnS

M— aeavable, fine and

Opaque to

black

coarse grained, com-translucent

Brownish black

Cuprite

Cubic

Adamantine

Reddish black

C — Octahedrons, dodeca- Dull

hedrons, alone or Translucent t in combination, opaque

compact,

MGrauular,

earthy

Tetragonal Vitreous Black

C— Square prisms with Translucent to Brownish

bipyramids opaque black H— Compact, dissemi-

:y

1. DASK GRAY OR BLACK Ht COLOR Hardness 3 to 6

Cleavage Fracture Tenacity

Characteriatica and

C — Brachypinacoidal 3.7 With other copper minerals;

F — Conehoidal 3.8 limonite, hematite.

Brittle

Olive green Dark brown eve

Brownish black Brittle Grayish black

F -Conchoids 1,

Fitch-hke appearance and fracture characteristic. Freeh material is hard and heavy. With lead, silver, bismuth minerals; also thorite, orthite, fergusonite.

— Rhombohedral , perfect, conspicu-

Curved crystals, cleavage, and rather high specific gravity characteristic. In ore deposits; beds and concretions in limestone and shale. With pyrite, chal copyrite, galena, tetrahedrite, cryolite.

Dark brown 4. Yellowish brown Gray

3.6 Brownish red 4. Dirty brown

C — Dodeca h edral perfect, usually conspicuous

F— Conehoidal

Brittle

C — Indistinct F — Uneven Brittle

Color and streak vary with impurities. When massive distinguished from siderite by cleavage. Extensively in limestone. With galena, chalcopyrite, pyrite, barite, fluorite, siderite, rhodochrosite.

Characterized by associates. With other copper minerals — malachite (green), azurite (blue), chalcoeit and melaconite (black, chalcopyrite (yellow), native copper.

4,6 Light orange C— Prismatic, not

F— Conehoidal

Brittle

Dark brown to black thorite sometimes contains a nucleus of yellow orangite; thorite believed to be decomposed orangite.

:y

Hiherals With Noh-Hetallic Ldster

Streak-

Sreen, red, yellow, or bl&ck

Name, Compoaition, and References

Crystallization Structure Crystals Massive -M

Luster Transparency

Color

Goelbite FeO.OH

Orthorhombic

C— SmaU, thin tabular, needle-like; paral-

Adamantine Dull

Translucent

Brownish

black Black

Paisons crusts

M— Reniform, stalactitic

Huebnerite

Monoclinic

Resm

Brownish

C— Long fibrous, bladed.

S bm tall

black

stalky; often divergent, without good terminations H — Compact, lamellar,

T lu nt t plaque

Black

granular

Wolframite

Submetallic

Dark gray

t— Thick tabular, short

Opaque

Brownish

columnar, often large M— Bladed, curved lam-black

Iron bUck

cellar, granular

Vitreous

Pitch black

C — Long prismatic.

SUky

Greenish

Silicate of Ca, Mg, Fe, Ai

etj'..

prism angle 124°;

black

often with rhomboopaque

Brownish

hedral-like termina-black

tions

M— Bladed, fibrous.

granular, compact

Monoclinic

Vitreous

Pitch bUck

C— Short prismatic;

Greenish black

Silicate of Ca, Mg, Fe, A!

etc.

Translucent to

Brownish

prism angle 87°

black

M— Compact, granular.

3S5

Amorphous T

Submetallic

Iron black

M— Botryoidal, reni-

Dull

Bluish black

MnO„ BaO, H,0, etc.

form, stalactitic;

Opaque

Dark gray

smooth surfaces

1. Dark Gray Or Black Hi Color

Hftrdnen 3 to B

4,6 Yellow C — Brachypinacoidal

6.6 Yellowish FUneven, tpiintery

brown Brittle

C — CliDopinacoidal, perfect, conspicu-

Structure, cleavage, and high specific gravity characteristic. lo quarts veins. With wolframite, fluorite, pyrite, echeelite, galena, tetrahedrite.

Dark reddish

C — Clinopinacoidal,

brown

Black

F— Uneven Brittle

Grayish green

CPriamatic, perfect,

Grayish brown

often coDspicuoua

Distinguished from huebnerite by streak. Powder may be slightly magnetic. With cassiterite, quarti, mica, fluorite, apatite, scheelite, molybdenite, hueb-

Simple, pseudohexagonal crystals, and cleavage at 124° important. Very common; in nearly all types of rocks. With calcite, quarts, feldspar, pyroxene, chlorite.

Pale green Grayish green

C — Prismatic, perfect,

conspicuous — 87° Brittle

Black F — Conchoidal,

Brownish black even

Brittle

Crystals usually eight-sided, more rarely four-aided; pseudotetragonal with prism angles of 87° and 93". Cleavage less distinct than on hornblende. Common in basic eruptive rocks and crystalline limestones.

Often with fine sooty coating of pyrolusite. With other manganese minerals; also limonite.

B. IHHERALS WITH HOH-HETAIXIC LUSTER Streak— Green, red, brown, yellow, or black

Crystallizatior Structure CryatalaC HaBBive — M

Transparency

Chromite

Cubic

Submetallic

Iron black

C— Octahedral, rare

Pitchy

Brownish

KiBiu, Duu,

pS

M— Compact, granular, disseminated grains

Opaque

black

Black

C— Tabular, rare

Greasy

Pitch black

H — Compact, granular, bladed, diasemi-iBtrod

Translucent to opaque

Brownish

black

grama

40S

Brookite

Adamantine

Iron black

TiO,

Metallic

Opaque

Reddish black Brownish black

Orthorhombic

Vitreous

Black

C— Columnar, acicular,

Submetallc

Greenish black

vertically striated

M— Compact with .radial

fibrous structure;

Opaque

Brownish black

granular

Stieak— Green, red, brown, yeUow,

or black

Monoolinic

Vitreous

Dark gray

H,FeAliO,

C— Tabular, six-sided M~Foliated, scaly, platy

Pearly

Greenish gray Greenish black

Tetragonal Adamantine Iron black

C — Prismatic, vertically Metallic Brownish

striated; twinned, Opaque to black

yielding knee-shaped transparent Reddish black or rosette forms M— Compact, dissemi-

:y

1. DARK GRAY OR BLACK m COLOR

Cleavage -C

Fracture Tenacity

Dark brown C — Indistinct

Grayish brown F — Uneven, conchoid-

May be slightly magnetic. Pitch' like appearance characteristic. With serpentine, chrome garnet, laratite; also in black sands, platinum placers.

Pale brown C — Pinacoidal, indis-

Grayish brown tinct

F — Uneven, conchoid-

C — Indistinct

F — Uneven Brittle

Often covered with yellowish or brownish alteration product Disseminated through the more acid igneous rocks; also in limestones. With magnetite, epidote, quartz, feldspar.

Crystals may be deeply striated; not twinned like rutile. With rutile, anatase, titanite, aduiaria, nephelite.

G.5 Blackish

C — Pinacoidal F — Uneven Brittle

Often covered with yellowish alteration product and, hence, softer. With dolomit, pyroxene, iron minerals.

HrdneSB orer 6

Pale green

C— Basal, perfect,

conspicuous F-Scaly Brittle

Pale yellow Pale brown

C— Prismatic, pyrar idai, not con spicuous

F— Uneven

Brittle

Sometimes softer due to alteration. Easily recognized by micaceous structure and perfect cleavage. In clay slates, mica schists. With corundum, garnet, chlorite, hornblende.

Often

Widely distributed. With quartz, feldspar, hematite, ilmenite, chlorite, brookite.

:y

B. MINERALS WITH NON-HETALLIC LDSTER Streak — Green, red, brown, yellow, or black

CryHtalKBatioi Structure Cryetflla -C Maeeive - M

Transparency

CASSITERITE Tetargonal

C — Thick prismatic; SnO, or SnSnO, knee-shaped twins

H — Compact, reniform, botryoidal, rounded UoHB pebbles, often with-

Kraiw, Dana. Pmoiu internal, radial

CORnHDlIM, variety Hexagonal Dull

Emera U — Fine to coarse gran- Submetallic

A1,0„ with Fe,0„ Fe,0„ 8iO, ular Opaque

Submetallic

BUck

DuU

Brownish

Translucent to

black

opaque

SPIHEL, varieties

Cubic

Vitreous

Black

Hercynite

C— Octahedral, smaU

Dull

Brownish

H — Compact, granular.

Nearly opaque

black

R" =Mg, Fe,

disseminated grains

Zn, Mn

R"'=A1, Fe

Is7. 338,

streak

— Dncolored, white, or light gray

GYPSUM, varieties

Pearly

Dark gray

C— Tabular, prismatic;

Black

CaS0,.2H,0 Safin spar

M— Cleavable, coarse

fibrous, foliated, earthy, sand

Silky Dull

Transparent to opaque

Cubic Vitreous Dark gray

C — Cubes, often skeletal Translucent to Black

or hopper-shaped nearly opaque

H — Compact, granular,

cleavable, fibrous,

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1. Dask Gray Or Black If Color

HacdneM over 6

Cleavage — C Fracture -F Tenacity

Pale browD

C— Indietinct

Pale yellow

F— Uneven

Brittle

Distinguished by high specific gravity. In veins cutting granite, gneiss; in alluvial deposits as stream tin. With quartz, wolframite, scheelite, arsenopyrite, molybdenite, tourmaline, fluorite, apatite.

C— Indistinct

brown

F — Uneven

Black

Brittle to tough

lagnetite.

Grayish green Pale brown

tinct F— Conchoidal BritUe

Hudnesa

WHte

perfect, conspicuous; pyramidal, orthopinacoidal

F-Conohoidal

Brittle, lamellie flexible

2.fi

White

C— Cubic, perfect

F— Conchoidal Brittle

iron ore. Powder may be magnetic. Properties vary with composition. With mica, amphibole, chlorite, spinel; in crystalline limestones, schists, peridotites.

3.9 Commonly in basic igneous rocks,

4.1 especially the olivine-bearing types. With olivine, serpentine, corundum, magnetite, hornblende, garnet.

Color due to organic material. Selenite, crjtals and cleavage plates; satin spar, fibrous, with silky luster. In limestones, shales. With halite, celestite, sulphur, aragonite, anhydrite, ore deposits.

Color due to organic matter. Characteristic cubical cleavage and saUne taste. May absorb moisture and become damp. With shale, gypsum, anhydrite, polyhalite.

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B. HUfERALS WITH NON-UETALLIC LUSTER

Streak— TTncolored, white, or light gray

Name, Composition, and References

Cryetallizatiou Structure Crystals "C Massive M

Traitsparency

APATITE, variety HexagoDal Dull

Phosphate rock H — Compact, fibrous, Opaque

Moses earthy

CRYOLITE Monoclinic Vitreous Brownish

C — Small, paeudocubical, Greasy black

AlF,,3NaP rare Translucent to Blackish

M — Cleavable, granular nearly

opaque

31S

C — Tabular, with hex- Submetallic Brownish

agonal or rhombohe- Transparent to black

dral habit opaque Greenish black H — Plates, disseminated

4B7,

Limestone Marble StagmiUe Travertine

Hexagonal Vitreous Dark gray

M — Cleavable, granular. Dull Brownish

fibrous, banded, Translucent to black

stalactitic, oolitic, opaque Black

porous, compact,

Streak— Uncolored, white, or light gray

Orthorhombic Vitreous Dark gray

C— Thick tabular, pris- Pearly Blackish

matic, rare Translucent to

M — Granular, compact, opaque

fibrous, lamellar,

cleavable

1. DARK GRAY OR BLACK m COLOR

Haidnesa 1 to 3

Cleavage -C

Fracture — F Tenacity

Specific Gravity

Characteristics and

F— Conchoidal, Brittle

More or leas impure "nasa's, frequently resembling compact bituminous limestone. Independent beds, nodules, or concretions.

White

C-Basal, prismatic, perfect, nearly

conspicuous F— Uneven Brittle

White Grayish

C— Basal, perfect,

Tough, lamelte of fresh biotite very elastic

White

Gray

C— Rhombohedral,

perfect F— Conchoidal Brittle

Often contains disseminated siderite, chlacopyrite, galena, pyrite, sphalerite, fluorite, columbite.

Easily recognized by structure, highly perfect cleavage, and elasticity. Important constituent of many igneous and metamorphic rocks — granite, syenite.

Rombohedral cleavage generally observed. Cleavages often striated. Yields bituminous odor when struck with hammer. Tp distinguish varieties, see refer-

CPinacoidal, perfect, .3 directions at ilO"

F— Conchoidnl

Brittle

Color due to organic matter. Pseudocubical cleavage sometimes noted. Granular varieties resemble marble. In limestones, shales. With halite, gypsum.

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B. HIHERALS WITH ROn-HETALUC LUSTER

Streak — Uncolored, white, or light gnj

Crystallization Structure Crystals -C Massive— M

CERDSSITE PbCO,

Knwu.,

Duim

aaa.

and

Psraoni

aaa

Orthorhombic

C— Tabular, prismatic, pyra midal; peeudohexagonal, clusters or star-shaped group

M— InterUced bundles, granular, stalactitic, compact, eartliy

Greasy

Silky

Translucent to opaque

Grayish black Black

SERPEirraiE H,Mgi,0,

Orthrohombic T C— Unknown

M— Compact, columnar, fibrous, lameUar, granular

Hexagonal

M— Compact, fibrous,

nodular, reniform,

earthy

Greasy Waxy Translucent to

opaque

Greenish black

Brownish black

APATITE, variety

Dull Opaque

Black

Orthorhombic C— Capillary, small M— Crusts, globular or

radial fibrous struc-

Vitreous

Black Dark gray

ture

Dolomite

Hexagonal

H — Coarsely crystalline,

compact, granular,

friable

Vitreous Translucent to opaque

Grayish black

Brownish black

M— Cleavable, fine or coarse grained, compact

Hexagonal

C— Rhombohedral, rare

MGranular, compact, earthy

Submetallic Opaque to translucent

Vitreous Dull

Translucent to opaque

Black Brownish

Yellowish

black

♦MAGHESITE MgCO,

Grayish black

black

lis.

35S.

1. dase: gray or black dt color

Cleavage -C Fracture — F

Tenacity

Gravity

Characteristics and

3. White 3.6 Gray

C— IndistiDct F — CoQchoidal Very brittle

Color due to admixture of fine particles of galena. Twinning, atnicture, luster, and bigh specific gravity characteristic. With lead minerals — galena, pyromorphite, anglesite; also malachite, limonite.

F— Conchoidal, splintery BritUe

F — Conchoidal,

Brittle

C— Pinacoidal, do-

F — Uneven, fibrous Brittle

Smooth and greasy feel. Ottn spotted, clouded, multi-colored. Sometimes crossed by seams of asbestos (chrysotile). With magnesite, calcite, chromite, garnierite, pyrope, platinum.

More or less impure masses frequently resembling compact, bituminous limestone. Independent beds, nodules, or concretions.

Secondary mineral, occurring on surfaces of rocks or minerals as crystalline crusts with pronounced radial fibrous s

3.6 White 4, Gray

C — Rhombohedral F — Conchoidal Brittle

C— Dodecahedral, perfect, usually conspicuous

F — Conchoidal

Brittle

C — Rhombohedral, perfect (crystals) F — Conchoidal, conspic-

Tough to brittle

Color largely due to organic matter; yields bituminous odor when struck with hammer; may be banded. In independent beds, fissures, and cavities; ore deposits.

Color and streak vary with impurities. Extensively in UmestoneS with galena, chalcopyrite, pyrite, barite, fluorite, siderite, rhodochrosite.

Conchoidal fracture generally prominent. Compact varieties apparently very hard. Disseminated in talcose and chloritic schists, serpentine, gypsum; independent deposits.

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B. Huterals With Hoh-Metallic Luster

StreRk— Uncolored, white, or light gray

Crystallisation

Structure Crystals -C Massive— M

Cubic Vitreoua Purplish

C — Cubes, alone or modi' Transparent to black

fled, well developed, nearly Brownish

common; penetraopaque black

I tion twins Black

a M — Cleavable, granular,

Huebnerite MnWO.

Monoclinic Resinous Brownish

C— Long fibrous, bladed, Submetallic black

stalky, often diver- Translucent to Black

gent, without good opaque

— Compact, granular

lamellar.

Monoclinic

C — Wedge-or envelopeahaped when disseminated; tabular or prismatic when attached

H — Compact, lamellar

Vitreous Submetallic Translucent to opaque

Black Brownish

HORHBLEHDE (Amphibole) Silicate of Ca, Mg, Fe, Al, etc.

Silicate of Ca, Mg, Fe, Al,

1 Hyperalhene

Monoclinic

Vitreous

Pitch black

C— Long prismatic, prism

SUky

Greenish

angle 124°, often

black

with rhombohedralopaque

Brownish

like terminations

black

M— Bladed, fibrous, granular

, compact

Monoclinic

Vitreous

Pitch

C— Short prismatic.

Submetallic

black

thick columnar.

Translucent to

Greenish

prism angle 87°

opaque

black

M— Compact, granular,

Brownish

disseminated

black

Orthorhombic

Pearly

Black

C— Prismatic, tabular.

Metalloidal

rare

Translucent to

black

M- — Granular, foliated.

Greenish black

cleavable aggregates

1. Dark Gray Or Black Ih Color

HardBMS 3 to 6

Hard-

Streak

Cleavage =-C Fracture -F Tenacity

Specific

Gravity

Characteristics and Associates

White

tect, conspicuous Brittle

Easily recognized by crystal form and octahedral cleavage. Common gangue mineral of metallic ores, especially galena, sphalerite, cassiterite; also with calcite, quarts, barite.

Greenish gray

C — Clinopinacoidal, perfect, oonepic-

Structure, cleavage, and specific gravity characteristic. In quartz veins. With wolframite, fluorite, pyrite, scheelite, galena, tetrahedrite.

White Gray

C— Prismatic, conspicuous partings often noted

F— Conohoidal

Brittle

With feldspars, pyroxenes, amphiboles, chlorite, scapohte, minion.

Gray

Greenish gray Browineh gray

C — Prismatic, perfect often conspicuous

Simple, pseudohexagonal crystals, and cleavage (124°) important.

types of rocks. With feldspars, quarts, pyroxenes, chlorite.

White Gray

—Prismatic, perfect, conspicuous — 87°

s.

White

C— Brachypinacoidal,

Gray

perfect, conspicuous

Brownish gray

F— Uneven Brittle

Crystals usually eight-sided, more rarely four-sided; pseudotetragonal with prism angles of 87° and 93°. Cleavage less distinct than on hombtende. Common in basic eruptive rocks and crystalline limestones.

Copper red iridescence often noted, due to small tabular inclusions. Commonly in the more basic igneous rocks. With feldspar (tabradorite), ohvine, hornblende, pyrrhotite, magnetite.

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B. Hdierals With Hoh-Hetallic Luster

streak

— Uncotored, white, or light gray

CryataUi.ation

Structure

Luster

Crystals -C Massive -M

Transparency

Black

C— Tabular, rare

Greasy

Pitch black

H — Compact, granular.

Translucent to

Brownish

Uobs

opaque

black

Knua, DuiB

Panoiui Sraina

Tetragonal

Metallic

Black

C— Pyraiilidal, tabular.

TiO,

rarely priHinatic

Opaque to

black

Reddish black

Broofcite

Orthorhombic

Adamantine

IrtHi black

Only in cryBtalB,— py-

Metallic

Reddish black

TiO,

Opaque to

Brownish black

matie, tabular

Perovskite

Pseudocubic

Black

-C — Apparently cubes.

Adamantine

Grayish

often Btriated H— Reniform aggregates,

Opaque

thick

Brownish

black

rounded grains

Streak

— white, or light gray

Triclinic

Vitreous

Daikgray

C— Thin tabular, often

Pearly

Greenish

Silicate of Na,Ca,Al

with rhombic crossaection M-Compact, cleavable.

Translucen

to nearly opaque

gray

granular

Honoclinic Vitreous Greenish

C — Prismatic, elongated Translucent to black and deeply striated opaque parallel to 6 axis; generally terminated on one end only H — Columnar, fibrous, parallel and divergent, granular

:y

1. Dark Gray Or Black Ih Color

Cleavage — C

Fracture — F Tenacity

Characteristioa and

S.5 Gray C — Pinacoidal, iodis-

Brownish gray F — Uneven, conchoidal

Brittle

Gray C — Indistinct

Yellowish white F — Uneven Brownish white Brittle

Often covered with yellowish or brownish alteration product. Disseminated through the more acid igneous rocks; limestones. With magnetite, epidote, quarts.

6.fi

Gray

C— Pyramidal, basa!

Crystals often resemble elongated

B.

White

F — Subconchoida 1 Brittle

octahedrons. With brookite, rutile, ilmenite, adularia, titanite, gold.

Crystals may be deeply striated; not twinned tike rutile. With rutile, anatase, titanite, adularia, nephelhe.

White Grayish

C— Cubical, fairly dis- 4,

tinct 4,1 F-Uneven Brittle

With chlorite, magneUte, limestone, serpentine.

Hardness over 6

White

C— Baaal, brachypina- 2,7 eoidal, periect,

conspicuous— 56"

Often with play of colors — yellow, green, blue, red. Inclined cleavages are striated. In basic igneous rocks. With pyroxenes, amphiboles.

Brittle

C — Basal, perfect F — Uneven Brittle

Crystals are often dark green or blackish green, massive aggregates lighter colored. Widely distributed. With quartz, feldspar, garnet, hornblende, pyroxene, prebnite, magnetite, native copper.

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B. lOHERALS WITH nOK-HETALUC LUSTER

Streak — Dncolored, white, or light gray

Crystallization Structure Cryetalfl -C

Massive -M

Monoclinic

C— Tabular, six-sided iO, M— Foliated, scaly,

Moaea plBty, granular;

Kraus. Dana, Parsons f"" *ld sheaf-like

Luster Transparency

Vitreous Dark gray

Pearly Greenish gray

Translucent to Greenish black opaque

Gadolinlle

Monoclinic

C — Prismatic, rough, r H — Compact, d i s s e i

Vitreous Black

Greasy Greenish

Translucent to black opaque

Tetragonal Metallic Iron black

C — Prisma tic, vertically Adamantine Brownish

striated; twinned, Opaque to black

yielding knee-shaped translucent Reddish black or rosette forms H — Compact, dissemi-

Cassiterite

Tetragonal

Submetallic

Black

C— Thick prismatic, knee-

Dull

Brownish

SnOj or SnSnO,

shaped twins, quite

M— Compact, reniform. botryoidal, rounded pebbles, often with internal, radial

Translucent to opaque

black

3i4, 249

fibrous structure

OAKHET, varieties

Cubic

Vitreous

Velvety black

C— Dodecahedrons, te-

Brownish

tragonal trisoctaheopaque

black

R"=Ca.Fe,Mg

drons, alone or in

R"'=Al,Fe

combination M — Granular, compact, lamellar, diBseminated

, sand

1. DAS£ GRAY OR BLACK IH COLOR Hanloess over 6

Cleavage ="C Fracture -F Tenacity

White C— Basai, perfect,

Greenish white spicuous

Gra5ish F— Scaly

Brittle

!s softer due to alteration. Easily recoguixed by micaceous structure and perfect cleavage. In clay slates, mica schists. With corundum, garnet, chlorite, hornblende.

Oreeniah gray

C— None

4,

In granitic rocks and pegmatites.

tery

With ferguBonite, orthite, fluorite, molybdenite.

Brittle

Gray

CPriamatic, pyramid-

Not as heavy as cassiterite. Often

YeUowish white Brownish white

dal, not conapicu-

F— Uneven Brittle

in hair-like inciuaions. Widely distributed. With quartz, feldspar, hematite, ilmenite, chlorite, brookite.

White C — Indistinct

Yellowish white F — Uneven Brownish white Brittle

Distinguished by high specific gravity. In veins cutting granite, gneiss; in alluvial deposits as tlreamtin. With quarts, wolframite, Bcheelite, molybdenite, tourmaline, fluorite.

C — Dodecahedral, i:

ally indistinct F — Conchoidal, une Brittle

AndradUe, commonly with magnetite, epidote, feldspars, nephelite, leucite; almandiU, with mica, ataurolite, andalusite, cyanite, tourmaline.

B. HinBRALS WITH hoh-metallic luster

Streak

— Uncolored, white, or light gray

References

Crystallization

Structure Crystals Massive -M

Luster

Transparency

Color

sio.

variety

Smoky quartz

Hexagonal

C— Prismatic, horizontally striated M — Compact, granular

Vitreous Transparent to translucent

Grayish black Brownish black

Cryptocrystalline

varieties

Chalcedony

Onyx

Flinl

Moees KrauB, Dana. 70. 324. 372

Hexagonal

Fine crystalline masses, banded, nodular,

botryoidat, stalactitic

Waxy

Vitreous Translucent to

opaque

GrayiBh black Brownish black

Velvet black

M'=Na, K, Li, Mg, Fe

Hexagonal

C— Prismatic, vertically striated; terminated with broken or rhom-

Pitchy Vitreous

opaque

Pitch black Brownish

black Bluish black

bohedral-hke surfaces; well developed crystals are hemimorphic H — Compact, divergent columnar

Staurolite

Orthorhombic Vitreous Brownish

C— Prismatic; twins plus- Dull black

( +) or X-shaped, Translucent to Dark gray

well developed, often opaque

SPINEL, varieties

Cubic

Vitreous

Brownish

C— Octahedral, well de-

Dull

black

veloped, common

Nearly opaque

Grayish black

R"-Mg, Fe, Dysluite

H — Compact, granular,

Greenish black

Zn, Mn

R"' AI, Fe

1 . DARK GRAY OR BLACK I H COLOR Hardness over 6

Cleavage — C Fracture -F Tenacity

Specific Gravity

Characteristic coachoidal fracture and glassy luster. Common in granitic rocks.

C — Indistinct

F — Conchoidal, e

spicuouB Brittle to tough

Conchoidal fracture characteristic. Chalcedony, waxy luster; onyx, banded; JliiU, generally with white coating; baaaniU, velvet bUck.

White

C— None

Spherical triangular cross-section,

Gray

F— Conchoidal, un- Brittle.

a

coal black color, and lack of cleavage important. In pegluvial

deposits- With quarts, feldspar, cosmterite, beryl, topas,

fluorite.

White

C— Brachypinacoidal

Fresh crystals usually possess

Gray

Brittle

bright and smooth faces, when altered dull, rough, softer, and

with colored streak- In metamorphic rock s — gneiss, m i'c a schist, slate. With cyanite, garnet, tourmaline, sillimanite.

White

C— Octahedral,

indis-

Commonly aa contact mineral in

Grayish

tinct F— Conchoidal

granularlimestones; in more basic igneous rocks; rouuded grains in pUcers. With calcite, chondrodite, serpentine, brucite, corundum, graphite, pyroxene.

B. Minerals With Hon-Hetallic Ldster

Streak— Dncolored, white, or light gray

Crystallization Structure Crtals-C Massive — M

Transparency

DIAMOND, varieties

DiamoTid proper C BoH

Carbonado

Cubic Adamantine Black

C — OetahedrowB, hexoc- Vitreous Dark gray

tahedroDS, usually Translucent to with curved surfaces opaque M— Rounded or irregular grains or pebbles, often with radial struc- Moaea ture

Ktaus, Duis, PananB

3se

1. DARK GRAY OR BLACK IH Hudneu over 8

Cleavage —C Fracture — F Teoacity

C — Octahedral, perfect

Characterietics and

Diamojid proper, crystals and cleavage fragmenta; bort, translucent with radial structure, also crystal fragments; carbonado, granular to compact, opaque. In serpentine rocks — kimberlite, peridotite — called bltie grouTui, or in placers. With pyrope, magnetite, chromite, cassiterite, sircon, gold.

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B. HOfERAIS WITH HOH-HETALLIC LUSTER

Streak— Pink, rd, brown, ot jeUow

Name, Composition, and Reterences

Structure

Cryrtala-C

Mflsaive-M

Luster

Transparency

Color

Bauxite

KmuB, M. 3B0.

Psreoni

Never in crystals M— Pisolitic, oolitic, rounded disBeminated graina, clay- Uke, earthy

DuU

Earthy Opaque

Red Reddish brown

HEMATITE, varieties

Redocher Fe,0, Oolite

Fi/siUiferou

H — Fine granular, earthy,

oolitic, replacement

of sheila

Dull Opaque

Brownish

red Cherry red

ae. 334.

Monoclinic Resinous Aurora red

C — Short prismatic, rare Transparent to Orange

H — Granular, compact, translucent yellow incrustations

Monoclinic Adamantine Crimson

C— Acicular, vertically Dull Peach red

striated, small, rare Transparent Pink H — Globular, reniform, to opaque

earthy, crusts, stains

Hexagonal Adamantine Scarlet red

C — Rhombohedral, thick Dull Brownish red

tabular, small Transparent to H — FinegranuIar,fibrous, opaque

earthy coatings

Proustite

Ag,AsS,

Hexagonal Adamantine Scarlet

C — Sniall, complex, rare Dull Vermilion

M-— Compact, dissemi- Translucent to

nated, crusts, bands transparent

Crocoite PbCrO,

Monoclinic Adamantine Hyacinth red

C — Prismatic, acicular Greasy Aurora red

M — Columnar, granular, Translucent

:y

2. PIHE, RED, OR RED VIOLET m COLOR

Cleavage -C Fracture — F Tenacitjr

Cherry red C — None

Reddish brown F— Earthy Brittle

Color and streak variable, due to pigments. Clay odor when breathed upon. Distinguished from clay by pisoUtic or oolitic structure. With clay or kaolinite in nodules, grains, or irregular deposits in timestoae or dolomite.

Red ocher, red earthy variety; ooWieftemnitte, fish-egg structure; foaaili/erota hematite, replacement of shells.

l.B Orange yelloi

C — Clinopinacoidal,

F — Conchoidal

Slightly sectile

Frequently disseminated in clay or dolomite. With orpiment, stibnite, native arsenic, pyrite, barite, calcite.

C- — C linopinacoidal ,

F— FbrouB, earthy Sectile, thin la mime flexible

Crystals frequently in spherical or stellate groups with velvety surface. Usually earthy. Color fades on exposure. Common alteration product of oobaltarsenie minerals — cobalt! te, smaltite, chloanthite.

C — Prismatic, not c

spicuous F — Uneven Brittle to sectile

C — Imperfect F — Conchoidal Brittle

C — Basal, prismatic F — Conchoidal, uneven Sectile

Characterized by color, streak, and high specific gravity (often lowered by gangue). Disseminated through silicious rocks. With native mercury, pyrite, marcasite, realgar, stibnite.

LigAf ruby sUver ore. Distinguished from cinnabar by associates. With pyrargyrite, in veins with other silver minerals and galena. Compare pyrargyrite

Resembles potassium bichromate in color. Alteration product of galena. With galena, quarts, pyrite, vanadiaite, wulfenite.

:y

B. BOnERALS WITH ROIf-HETALLIC LUSTER

Streak— PJnk, red, brown, o

Crystallization id Structvire

CryatalB-C Maaaive - M

Tranaparency

Pyrarynte

Hexagonal

C— Small, complex, rare

K— Compact, diBBeminated

, crusts, bands

Adamantine MetalUc Transparent to opaque

Dark red

Dua.

13S.

Ml.

26S

Tetragonal

C— Square, thin tabular, more rarely pyramidal

M— Coarse, fine granular

Resinous Adamantine Transparent to

Orange red Bright red

Vanadinite

2S1

Hexagonal

C— Prismatic, small, at

times skeletal M — Compact, globular,

fibrous, crusts

Resinous Translucent to opaque

Ruby red Brownish red Orange red

Streak— Pink, red, brown, or yelknr

BEHATITE, varieties

Hexagonal

Submetallic

Brownish red

m

H— Compact, granular.

Dull

Dark red

Fe,0, Compact

columnar, splintery, radiated reniform or

Opaque

8e, 334.

botryoidal

Sphalertte

Cubic

Greasy

Brownish

C— Tetrahedral, common

red

ZnS

M— Cleavable, fine to coarse granular, com-opaque

Yellowish red

pact

Coprtte

Cubic

Adamantine

Cochineal red

C— Octahedrona, dodeca-

Dull

Brick red

Cu,0

hedrons, alone or in

M— Granular, earthy; slender crystal ag-

Translucent to opaque

Dark red

3. Pikk, Red, Or Red Violet Is Color

Hardneas 1 to 3

Cleavage ="0 Fracture -P Tenacity

2.6 Cherry red 3. Purplish red

C — iDdiatinct F — Conchoidal Brittle

Frequently as gray or dark red bands. Darker than proustite dark rubj/ silver ore. With proustite, in veins with other silver minerals and galena.

Lemon yellow C — Pyramidal, india- Pale yellow tinct

F — Conchoidal, uneven

Brittle

Square plates, sometimes with . forms of the third order. With lead miaerala — galena, pyromorphite, vanadinite.

C— None

F — Conchoidal,

Brittle

Crystal faces smooth with sharp edgea. With lead minerals but never in large quantities.

Cherry red C — None

Reddish brown F — Uneven, splintery Brittle

ArgilloMous hematite, impure from clay, sand, jasper; compact hematite, usually quite pure.

— Dodeeahedral, perfect, usually con-

Pale yellow Brownish yellow

Brownish red C — Indistinct

Dirty brown F — Uneven

Brittle

Color and streak vary with impurities. Extensively in limestone. With galena, chalcopyrite, pyrite, barite, fluorite, siderite, rhodochroaite.

Characterized by associates, copper minerals — malachite (green) azurite (blue), chalcocite and melaconite (black), chalcopjrrite (yellow), native copper.

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B. HIirERALS WrrH HOH-BIETALLIC LUSTER Streak — Pink, red, tn'own, or yellow

Name, Composition, and

Structure Crystals -C Massive — M

Transparency

Zincite

Hexagonal

Adamantine

Dark red

C— Heminorphic, rare

Vitreous

Blood rM

ZnO

H — Compact, granular, MiBM foliated

Translucent to opaque

Kraiu.

Dana.

Famous

S4.

Xenotime

Tetragonal

Greasy

Flesh red

C— Pyramidal, prismatic

Vitreous

Brownish red

M— Compact, disseminated, rounded

Translucent to opaque

Yellowish red

lae,

grams

Goethite

Orthorhombio

Adamantine

Reddish

e-mail, thin tabular,

Dull

Brownish red

FeO.OH

needle-like; paral-

Translucent

belly grouped or scaly, to opaque fibrous, velvety (Moists M— Reniform, stalactitic

Huebnerite MnWO.

Wolframite

Rotile

TiO, or TiTiO.

Monoclinic Greasy

C — Long, fibrous, bladed, Submetallic

stalky; often diver- Translucent

gent, without good to opaque

M — Compact, lamellar,

granular

Monoclinic Submetallic

C — Thick tabular, short Opaque

columnar, often large H — Bladed, curved lamellar, granular, corn- Tetragonal Adamantine C — Prismatic, vertically Submetallic striated; twinned. Translucent yielding knee-shaped opaque

M — Compact, disaemi-

:y

3. PHTK. RED, OR RED VIOLET Iff COLOR

HardnesB over 3

Cleavage — C Fracture -F Tenacity

4. Orange yellow 4.S Beddish yellov

C — Basal, sometimes

conspicuous F— Uneven

Brittle

Associates important — calcite, franklinit (black), willemite (yellow to green), rhodonite (flesh red). On exposure becomes coated with the white carbonate.

Pale brown C — Prismatic

Yellowish F — Uneven, splintery

Reddish Brittle

4.B Yellowish C — Brachypioacoidal

6.6 Yellowish brown F — Uneven, splintery Brittle

Commonly as loose, disseminated, or attached crystals resembling zircon, but softer. In granite and gneiss with zircon; alluvial deposits.

Usually with other iron minerals; in cavities in hematite or limonite.

Yellowish brown C — Clinopinacoidal, perfect, conspicuous Brittle

Structure, cleavage, and specific gravity characteristic. In quarts veins. With wolframite, fluorite, Bcheelite, galena, tetrahedrite.

C — Clinopinacoidal, perfect, conspic-

Distinguished from huebnerite by streak. Powder may be slightly magnetic. With cassiterite, quart, mica, scheelite, molybdenite, huebnerite.

C — Prismatic, pyramid-

FUneven Brittle

Not as heavy as cassiterite. Often in fine, hair-like inclusions. Widelydistributed. Withquarta, feldspars, hematite, ilmenite, chlorite, brookite.

:y

B. UHERALS WITH HOIf-HETALUC LUSIXR

Streak — Pinl red, brown, or yellow

Name, Composition, and Referencea

Crystallisation Structure Crystals Massive

Luster

Transparency

CASSITEKITE Tetragonal Adamantine

C — Thick priematic ; knee- Dull SnO, or SnSnO, shaped twins quite Trauelucent to

common opaque

H — Compact, reniform, botryoidal, rounded Moses pebbles, often with

Kiaue, Daa, PareonB radial fibrous struc-

Streak—Uncolored, vfbite, or light gray

Camallite

Orthorhombic

Vitreous

Reddish

C— Apparently hexago-

Dull

MgCl,.KC1.6H,0

nal, rare

Transparent to

H — Compact, granular

translucent

DuD

Pink

H — Earthy, powdery

Opaque

Red

Monoclinic

Dull

Reddish

C— Scaly, with hexago-

Pearly

H.Ali,0,

nal outline, rare

Opaque to

M— <;ompact, friable.

translucent

clay-Uke

♦ TALC, varieties

Monoclinic

Greasy

Reddish

C— Thin tabular, indis-

Pearly

tinct

Translucent to

K— Foliated, globular.

opaque

fibrous, granular.

compact

Gypsuh

Monoclinic

Vitreous

Flesh red

C— Rare

Silky

Brick red

CaS0,.2H,O

M — Coarae, fine granular, Dull

fibrous, cleavable, Transparent to

sand opaque

:y

2. , RED, OR RED VIOLET HT COLOR Hardness over 3

Cleavage -C Fracture — F Tenacity

C — Indistinct F — Uneven Brittle

Specific Gravity

Recognized by liigh specific gravity. In veins cutting granite, gneiss; in alluvial deposits as stream tin. With quarta, wolframite, scheelite, arsenopyrite, tourmaline, fiuorite, apatite.

Hardness 1 to 3

C — Indistinct F — Conchoidal Brittle

2.6 YeUowish white F— Earthy, conspicu- Reddish white ous

Brittle

1. White C— Basal, perfect, con-

2.5 Reddish white spicuous when foliated

F — Uneven, splintery Sectile, lamise flexible

C — Clinopinacoidal, , perfect conspicuous; pyramidal, orthopinacoidal (crystals)

F — Conchoidal

Brittle, lamicuB flex-

Color due to henlatite or goethite. Bitter taste; absorbs moisture. With halite, kieserite, kainite, sylvite, anhydrite.

Harder when fresh and unexposed. In cavities and fissures in basic igneouB rocks. With stilbite, apophyllite, analcite, native copper.

Clay odor when breathed upon. Usually adheres to tongue and becomes plastic when moistened. Greasy feel. With quartz, feldspar, corundum, diaspore.

Greasy or soapy feel important. FoluUed, easily separable, inelastic plates, H— 1; s'oapaione or steatite, coarse to fine granular, more or less impure, H up to 2 . 5. With serpentine, chlorite, dolomite, magnesite, actinolite.

Ferruginous gypsum. In limestones, shales. With halite, celestite, sulphur, aragonite, anhydrite, ore deposits.

ible

:y

B. HIIfERALS WITH NOIT-BIETALLIC LUSTER

Streak— Uncolored, white, or gray

Name, CompositioQ, and EeferenceH

Structure

OryBtaU-C

MaBsive-M

Luster Transparency

Color

S;lite Cubic

C— Cubes, alone or with KCl octahedron

Mosea M— Granular, compact KnoM. Diuu., PDB 98, 318, 310

Vitreous Transparent to

Red Yellowish red

Cubic

C— Cubes, often skeletal or hopper-shaped,

Transparent to translucent

Red Reddish

Purplish

M— Compact, cleavable, granular, fibrous, crusts, slalactitic

Monoclinic

Pearly

Pink

C— Short prismatic

Translucent

Rose red

M— Granular, coarse or fine; scales, cleavable

Red violet

2 Is, 487,

plates

Monoclinic

Vitreous

Flesh red

C— Thick tabular

Greasy

Brick red

NaO.CaSO.

M— RenHorm, lamellar

Transparent to

Amorphous

Greasy

Brownish red

M— Irregular, stalactitic

Transparent to

Yellowish red

C,„H„0.

grains and lumps

translucent

3Sg

Monoclinic

Vitreous

Flesh red

C— Tabular, prismatic,

Transparent to

Brick red

MgS0,.KC1.3H,0

M— Compact, fine granular

translucent

Vitreous

Reddish

C— Tabular, pseudohex-

Pearly

agonai, rare

lary, surface smooth, internal structure

Translucent

fibrous

. Uncommon color.

2. Pure, RED, OR RED VIOLET Df COLOR Hsrdaess 1 to 3

Cleavage -C Fracture — F Tenacity

Characteristics find

C— Cubic F— Conchoidal Brittle

Color due to impurities. Salty bitter taste. May absorb moisture and become damp. Ueually in salt deposits. With halite, kainite, camallite.

White

C— Cubic, perfect, con-

Characteristic cubical cleavage and

spicuous F-Conchoidal Brittle

saline taste. Color due to impurities. Hay absorb moisture and become damp. With shale, gypsum, anhydrite, polyhalite.

White

CBaaal, perfect

F— Scaly, granular Tough

ular limestone. In pegmatites, granites, gneisses. With red tourmaline (rubellite), amblygonite, spodumene, topaz.

White

C— Baaal, perfect

Bitter saline taste. On exposure

F — Conchoidal

becomes coated with white pow-

Brittle

dery crust. With halite, thenardite, mirabilite.

3.S

White

F— Conchoidal

Fossil resin. Electrified when

Brittle

rubbed. Often mottled and inclusions— insects, vegetable

remains, liquids, minerals.

White

C — Pinacoidal, pris-

Taste, salty, bitter, and astringent.

matic, not conspic-

Uoub

F— Uneven

Non-hygroscopic. With halite, sylvite.

Brittle

White

C — Basal, not conspic-

Strong clay odor when breathed

upon. With bauxite, natrolite, limonite, corundum.

B. HIWERALS WITH HOK -METALLIC LUSTER Streak — Uncolored, white, or light gray

CryHtUisation itioD, and Structure Lueter

ceB Crystals C Transparency

Massive

C — Tabular, prismatic, Submetallic hexagonal or ortho- Transparent rhombic outline, translucent often large and coarse Mosea M — Plates, disseminated Pmon. scales

4ie

Copper red Bronze red Brownish red

*Cryolite

AlFj,3NaF

Vitreous Reddish

Greasy Brownish red

rare Transparent to Brick red

— Cleavable, granular translucent

Calcite

Wulfenite PbMoO.

Uncommon color.

Orthorhombic Vitreous Reddish

C — Tabular, prismatic. Pearly Red

very common; crest- Transparent to

ed divergent groups opaque

M — Compact, lamellar,

fibrous, cleavable,

reniform

Hexagonal

Vitreous

Pink

C— Scalenohedral, rhom-

Dull

Red

bohedral, prismatic,

Transparent

Violet

tabular, often highly

to nearly

Amethystine

modified and

opaque

twinned

M— Cleavable, granular,

Tetragonal Greasy Orange red

C — Square, thin tabular, Adamantine Bright red

more rarely py- Transparent to

ramidal translucent M — Coarse to fine granular

:y

2. Pirk, Red, Or Red Violet Dt Color

Cleavage — C Fracture — F Tenacity

Characteriatice and

C — Basal, perfect, con

spicuoua Tough, tamiiue very

elastic

When cleavage laminfe are held close to the eye in viewing a source of light, a star-like form is Bometimes observed. Especially characterletic of crystalline lime- Btones, dolomites, Bchists. With pyroxenes, amphiboles, serpen-

White

C— Basal, prismatic,

perfect, nearly 90°,

siderite, chalcopyrite, galena, sphalerite, fluorite, columbite.

F— Uneven

Brittle

White

C— Basal, prismatic,

F— Uneven Brittle

Characterized by rather high specific gravity and cleavages. In metalliferous veins; pockets and lenticular masses in limestones. With galena, sphalerite, fluorite, chalcopyrite; manganese and iron minerals.

White

C— Rhombohedral,

perfect, very conspicuou

B F— Conchoidal Brittle

Rhombohedral cleavage characteristic, especially on crystals. Cleavages often show stria tions. Very strong double refraction observed when transparent.

White C — Pyramidal, indis-

Yellowish white tinct

F — Conchoidal, uneven

Brittle

6.3 Square plates, sometimes with 7 . forms of the third order. With

lead minerals — galena, pyromorphite

, vanadinite.

:y

BUHERALS WITH VOH-HETALLIC LUSTER Streak — Uncolored, white, or Ugbt gray

Crystallization Structure Crystals -C Massive— M

iranadialte Hexagooal Greasy Ruby red

C — Prismatic, small, at Translucent to Orange red I

times skeletal opaque Brownish red I

Kmua. Dana, PtuMog H— Compact, globular, 173, 600. 2M fibrous, Crusts

Streak— Uncotored, wUte, or light gray

Monoclinie

Vitreous

Reddish

Pearly

agonal, rare H— Stalactitic, mammillary, surface smooth, internal structure

Translucent

Monoclinie 7

Greasy

Flesh red

C— Indistinct

Pearly

Brick red

K--Compact, fibrous,

Translucent

lamellar

Aithydrite

Orthorhombic

Vitreous

Reddish

C— Thick tabular, pris-

Pearly

Brick red

matic, rare

Translucent to

H— Granular, compact,

opaque

fibrous, lamellar.

Celestite

Orthorhombic

Vitreous

Reddish

C— Tabular, prismatic.

Pearly

Brick red

common

Transparent to

M — Compact, cleavable.

translucent

fibrous, granular.

Orthorhombic Vitreous

C — Tabular, prismatic, Pearly

very common; crest- Transparent

ed divergent groups opaque

M — Compact, lamellar,

fibrous, cleavable,

reniform

:y

3. PniK, RED, OR RED VIOLET IN COLOR HardncM 1 to 3

Cleavage -C Fracture -F Tenacity

hit

C— None

ello

wish white F— Conch oidal, unev

en 7.2

Brittle

Crystal faces smooth with sharp edges. With lead minerals but never in large quantities.

C— Basal, 1

uous Tough

Strong clay odor when breathed upon. With natrolite, limonite, corundum.

White P— Stalky,

Reddish white Brittle Yellowish white

Taste, bitter and astringent, but weak. With halite, anhydrite,

sometimes conspicresemble

marble. Not as heavy aa celestite or barite. In limestones, shales. With halite, gypsum.

C — Basal, prismatic,

conspicuous F— Uneven Brittle

Heavier than calcitc, anhydrite; lighter than barite. In limestones, dolomites, shales. With gypsum, aragonite, halite, galena, sphalerite.

C — Prismatic,

spicuous F — Uneven Brittle

Characterized by rather high specific gravity and cleavages. In metalliferous veins; pockets and lenticular masses in limestones. With galena, sphalerite, fluorite, chalcopyrite; manganese and iron minerals.

B. boherals with noh-hetaluc lusir

streak— Uncolored, wMte, or Ught gray

Crystallization Structure Crystals— C Massive - M

Transparency

Monoclinic Vitreous Pale red

C— Twinned in sheaf-like. Pearly Brick red

radial, or globular Tranaparent to aggregates translucent

a ' 281. 4M. 414

I Laumontite

Monoclinic Vitreous Flesh red

C — Tabular, striated Pearly Brick red M — Foliated, granular, Transparent to

globular translucent

Monoclinic Vitreous Pink

C~Columnar Dull Red

H— Radial, divergent. Transparent to

earthy opaque

SERPEHTIHE H,Mgi,0,

Hargarite

Orthorhombic ? Greasy Brownish red

C — Unknown Waxy Red

H — Compact, columnar, Translucent to

fibrous, lamellar, opaque granular

Monoclinic Pearly Pink

C — Short prismatic Translucent Rose red

H — Granular, coarse or Red violet

fine; scales, cleavable plates

Monoclinic Pearly Pink

C — Six-sided scales. Vitreous Rose red

plates Translucent M— Scaly, foliated, gran- Hexagonal Vitreous Pink C — Rhombohedral with Transparent to Reddish

curved surfaces translucent M — Coarsely crystaUine,

compact, granular,

Uncommon color.

S. PDIK, RED, OR RED VIOUTT Df COUIR

Cleavage — C Fracture — F Tenacity

Specific Gravity

Characteristic and Associates

C — Pinacoidal

F — Uaeven Brittle

Radial and sheaf -like structure important. In basic igneous rocks, ore deposits. With chabazite, apopbylUte, heulandite, datoUte, calcite.

C — Clinopi oaooidat ,

F — Uneven Brittle

C — Clinopinacoida 1,

prisroatic F — Uneven, earthy Brittle, friable

F— Conchoidal, splin

tery Brittle

In basic igneous rocks and metalliferous veins. With chabasite, stilbite, apophyllite, datolite.

On exposure becomes dull and crumbles to powder. In cavities and fissures in basic igneous rocks. With stilbite, apophyllite, analcite, native copper, epidote.

Smooth and greasy feel. Often spotted, clouded, multicolored.' Color due to unusual amount of ferric oxide. With maguesite, calcite, chromlte, gamierite, pyrope, platinum.

C— Basal, perfect

When massive often resembles

F— Scaly, granular

granular limestone. In pegma-

Tough

tites, granites, gneisses. With red tourmaline (rubellite), amblygonite

, spodumene, topaz.

C— Basal, perfect, eon

3,

Resembles the micas in structure

and cleavage, but harder, lamin

F— Scaly, granular

brittle and inelastic. With

Brittle

chlorite, corundum, emery, diaspore.

Crystals generally curved or sad-perfect

dle-shaped. Marble includes

F— Conchoidal

some compact varieties. In in-

Brittle

dependent beds; fissures, and cavities; with ore deposits.

B. HinERALS WITH VOH-KETALLIC LUSTER

Streak

-Uncoloreil, white, or Uht gray

Crystallization

Name, Composition,

and

Structure

Luster

Reference!,

Crystals Massive -M

Transparency

Aragohite

Orthorhombic

Vitreous

Reddish

C— Chisel-or spear-shap-

Greasy

Brick red

u™

ed; pseudohexagonal prisms ; radial, columnar or aeicular

Transparent to translucent

M— Stalactitic, renitorm,

crusts, oolitic

Sphalerite

Cubic

Greasy

Brownish red

C— Tetrahedral, common

Submetallic

YeUowish red

ZnS

M-Cleavable, fine or

opaque

pact

Hexagonal

Vitreous

Rose red

C— Rhombohedral, rare

Brownish red

H — Cleavable, granular, compact, botryoidal.

Pink

Vitreous

Red violet

C— Cubes, alone or modi-

Transparent

Pink

CaF,

fied, well developed, common; penetration twins M— Cleavable, granular,

to nearly

opaque

Rose red

fibrous

Hexagonal

Vitreous

Flesh red

C— Rhombohedral, cube-

Translucent to

Red

etc.

like, lenticular

transparent

I *Haimotome

BaAli,0„.6H,0, etc.

Monoclinic C— Usually t trating a

Vitreous , pene- Translucent

Xenotime YPO.

Tetragonal Greasy Flesh red

C — Pyramidal, prismatic Vitreous Brownish red

H — Compact, dissemi- Translucent to Yellowish red

nated, rolled grains opaque

:y

2. PINK, RED, OR RED VIOLET IH COLOR Hardneu 8 to 6

Cleavage — C Fracture -F Tenacity

White Gray

prismatic F — Conch oidal Brittle

Gray Yellowish white

C— Dodecahedral, perfect, usually

F~Conchoidal

Brittle

White

perfect, conapicu-

F— Uneven Brittle

White

C— Octahedral, per-

Brittle

' Twins common, often pseudohesagonal

(prism and striated base). In cracks and cavities, disseminated; with ore deposits; deposition from hot springs; in shells. With gypsum, celestite, sulphur, siderite, leolites.

Color and streak vary with impurities. Extensively in limestones. With galena, chalcopyrite, pyrite, barite, fluorite, rhodochrosite.

May turn brown to black on exposure, due to MnO,. With galena, sphalerite, pyrite, alabandiie, rhodonite, psilomelane, silver ntinerals.

Easily recognized by crystal form, cleavage, and hardness. Common gangue mineral of metallic ores. With galeoa, sphalerite, cassiterite. calcite, quartz, barite.

C— Rhombohedral, not conspicuous F— Uneven

Brittle

C — Pinacoidal F— Uneven Brittle

Yellowish white Brownish white Reddish white

C — Prismatic

F — Uneven, splintery

Brittle

Generally in cube-Uke crystals. Inferior cleavage distinguishes it from fluorite and calcite. In basic igneous rocks. With analcite, stilbite, harmotome, heulandite.

Cruciform twins. In basic igneous rocks and metalliferous veins. With chabasite, calcite, adularia, quartz. Pkillipaiie, contains calcium replacing barium.

Commonly as loose, disseminated, or attached crystals resembling zircon, but softer. In granite, gneiss. With zircon; alluvial deposits.

B. HmERALS WITH flOK-HETALLIC LUSTER

Streak — Uncolored, white, or light gray

Crystallization Structure Crystals -C

Luster TranHparency

Tetragonal Adamantine

C— Pyramidal, small; Greasy

tabular Transparent to MoH H — Druay crusts, reni-translucent

Kmus. Daoa. Panoiis form, granular, dis-

Tetragonal Vitreous

C — Prismatic, pyramidal. Pearly

paeudocubical, tabu- Transparent lar to nearly

H— Lamellar, granular, opaque compact

Pale red Flesh red Rose red

Wollastonite, (Pyroxene, tabu- Monoclinic Vitreous Reddish

lar spar) C — Tabular, prismatic . Silky

CaSiO, H — Cleavable, fibrous, Transparent to

granular, compact translucent

Apatite

Hexagonal

Greasy Viole

C~Prismatic, thick tabu-

Vitreous Brow

Translucent to Red

times large with

opaque

rounded edges

M— Compact, fibrous,

nodular, reniform

Huebnerite

Monoclinic

Resinous Brow

C— Long fibrous, bladed,

Submetallic

stalky; often divergent

, without good

opaque

M— Compact, lamellar,

granular

3. Pihk, Red, Or Red Vioit Ih Color

Hardness 3 to 6

Cleavage 'C Fracture ""F Tenacity

C — Pyramidal F— Conchoidal, Brittle

Small, well developed octahedrallike crystals, ueually on quartz; when massive, high specific gravity important. With wolframite, caasiterite, fluorite, topaz, molybdenite.

C — Basal, perfect,

apicuouB F — Uneven

Brittle

Prism faces vertically striated. In fissures and cavities in basic igneous rocks. With natrolite, analcite, laumontite, datolite, pectolite, native copper, calcite.

C — Basal, orthopinacoidal

F— Uneven

Brittle

Fibers may be parallel or divergent. Typical contact mineral. Often in crystalline limestone, with garnet, dioside, vesuvianite, epidote, graphite.

C — Basal, imperfect F— Conchoidal, uneve:

Brittle

Crystals may be vertically striated and have fused appearance. Color often unevenly distributed, — mottled brown and green. In crystalline limestones, metalliferous ore deposits, igneous rocks. With quartz, cassiterite, fluorite, wolframite, magnetite.

C — Clinopinacoidal , perfect, conspicu-

Structure, cleavage, and specific gravity characteristic. In quartz veins. With wolframite, fluorite, pyrite, scheelite, galena, tetrahe-

B. MniERAi WITH hou-metallic luster

Streak — Uncokired, white, or gnj

Name, Composition, and

Structure

References

Crystals -C Massive -M

Transparency

&quot;Ahalcite

Cubic

Vitreous

Reddish

C— Tetragonal trisocta-

Translucent to

Brick red

hedrons, cubes

Moeea

H — Granular, compact

EnuB, Duu. Panon

Orthorhombic

Vitreous

Reddish

C— Slender prismatic,

Silky

nearly square, radial

Transparent to

or interlacing groups

MFibrouB, granular,

compact

Thom80ii!te

Orthorhombic

C— Prismatic, vertically

Vitreous

Silky

Reddish

striated, divergent

Pearly

5H,0

groups H — Fibrous, columnar, radial; spherical con-

Translucent to transparent

cretions

M — Compact, fibrous, granular, botryoidal

Vitreous Pink

Greasy Red

Dull Red violet

Translucent to opaque

Monoclinie Vitreous

C — Wedge-or envelope- Greasy

shaped when dissem- Transparent inated; tabular or opaque

prismatic when attached H — Compact, lamellar

Monoclinie Resinous Hyacinth red

C — Thick tabular, square Vitreous Brownish red

prismatic Translucent to

H — Angular, rolled opaque

:y

3. Pink, Red, Or Red Violet Ir Color

Hardness 3 to S

Cleavage — C Fracture -F Tenacity

C — None

F— Uneven, conchoid-

C — Priematic F — Uneven Brittle

Good cryetala common. In fissures and cavities in basic igneous rocks. With apophyllite, chabasite, natrolite, laumontite, datolite, native copper, prehnite, epidote.

Crystals have nearly square crosssection. With chabazite, analcite, apophyllite, stilbite, prehnite, datolite.

C — Pioacoidal

F— Uneven Brittle

When massive, radial fibrous, often mottled or banded. In fissures and cavities in basic igneous rocks. With stilbite, analcite, prehnite, calcite.

6. White 5.6 Gray

C — Priamatic, conspicuous parting often noted

F— Conchoidal

Brittle

Compact masses often with brownish, yellowish, or whitish streaks and spots. In cracks and cavities in basic igneous rocks. With calcite, prehnite, epidote, native copper, zeolites.

With feldspars, pyroxenes, amp hiboles, chlorite, scapolite, zircon.

Crystals commonly small, highly

modified, or as rolled grains in sand. With magnetite, lircon, garnet, thorite, gold, chromite, diamond.

:y

B. mifBRALS WITH HOH-CBTALLIC lusier Streak— Uncolorcd, white, or Ut gray

CryetaUiiation Structure CryBtals -C MaBsive— M

MoKB Dated grains, nodular

'Cancrinite Hexagonal

C — Prisma tie, rare M— Compact, lameUar, columnar, dissemi- 333, 411. 395 nated

elaeolite) C— Short prismatic, {Na,K),AI,Si,0,. tabular

M — Compact, disseminated grains

/ nNaAli,0„Cl

Tetragonal C — Prismatic H — Compact, granular fibrous, columnar

Vitreous Pink

Greasy Reddish

Transparent to translucent

Greasy Reddish

Vitreous Rose red

Traospareat to translucent

Greasy Reddish

Vitreous Brownish red

Transparent to Brick red opaque

Vitreous Pink

Greasy Red violet

Translucent Brick red

Hexagonite C — Bladed, without CaMg,(8iO,)i

terminations H — Compact, columnar,

fibrous Triclinic C — Tabular, prismatic,

rounded edges, often

H — Compact, cleavable, granular, disseminated grains

Hexagonal

C— Prismatic

M— <mpaet, granular, disseminated grains

Vitreous Pink

Silky Red violet

Transparent to Lavender translucent

Vitreous Brownish red

DuU Flesh red

Transparent to Rose red opaque

Greasy Fle red

Vitreous Brownish red

Transparent to

opaque

:y

2. PIHK, RED, OR RED VIOLET llf COLOR Hardness 3 to 6

C — Dodecahedral F — Conchoids 1, un

Characteristics and

Recognized by associates — nephelite, cancrinite, leucite, feldspar, zircon; not with quartz.

C— Prismatic, perfect F— Uneven Brittle

Typical associates — nephelite, Bodalite, biotite, feldspar, titanite.

C — Prismatic, not

conspicuous F— Conchoidal Brittle

C — Prismatic, perfect, conspicuous — 124° Brittle

Distinguished from orthoclase by interior cleavage, and more greasy luster. With feldspars, cancrinite, biotite, Bodalite, zircon, leucite, corundum; not with

Often resembles pink fluorite in color, but cleavage less distinct, and harder. In metamorphic rocks, especially gi'snuiar limestones. With pyroxenes, apatite, garnet, titanite, biotite, amphiboles.

Silky luster and distinct cleavage {124°) important. In limestones, dolmites; also schists.

Tough, when

crystals brittle

May be stained brown to black on exposure, FowlerUe, variety containing zinc. With Iranklinite, zincite, willemite, calcite, tetrahedrite.

C — Basal, prismatic F — Uneven Brittle

Crystals of willemite small, those of Iroostite — manga nifero us variety — often large. Characterized by associates — franklinite, z incite, rhodonite, calcite.

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B. HIHERALS WITH ROn-HETALLIC LUSTER

Streak— Uncolored, white, o

light gr.y

Name, Compoeition,

and

Crystalliuation Structure CryBtala -C Massive -M

Luster Transparency

Color

OPAL, varieties

Fire opal Opal jasper SiO,.xH,0

Amorphous Vitreous M— Renifonn,botryoidftl, Greasy

stalactitic, compact Transparent to opaque

sad

Red Brownish red

Streak— Dncolored, white, or light gray

Chondrodite

Rutile

TiOj or TiTiO.

Monoclinic

C — Prismatic, thick tabular; twins; often large

H — Cleavable, granular, disseminated

Monoclinic

C — Small, highly modified, rare

M — Rounded, disseminated grains; com-

Orthorhombic

C — Prismatic, deeply striated, bent, without good termination

M — Columnar, broad bladed, fibrous

Monoclinic

H — Columnar, fibrous, parallel and divergent; granular

Tetragonal

C — Prismatic, vertically striated; twinned, yielding knee-shaped or rosette forms

M — Compact, dissemi-

Vitreous Flesh red

Pearly Brick red

Translucent to opaque

Vitreous Brownish red

Greasy Dark red

Translucent to

opaque

Vitreous Red

Transparent to opaque

Adamantine Dark red Submetallic Brownish red

Translucent to opaque

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a. PIHK, RED, OR RED VIOLET IH COLOR Hardness 3 to 6

Cleavage — C Fracture -F Tenacity

Specific

Gravity

White

F— Conchoidal

spicuous Brittle

Structure and fracture characteristic. Fire opal, transparent to translucent and red; opal jasper, greasy and opaque, resembling jasper. In veins, cavities, and masBea of irregular outline.

C — Basal, clinopinacoidal, perfect, conapiouo us — 90°

F — Conchoidal, un-

Brittle

C— Basal

F — Conchoidal, i

Characterized by rectangular cleavage and absence of twinning striations. In granitic rocks. With quartz, other feldspars, mica, hornblende, zircon.

Associates important. Chiefly in crystalline limestones and dolomites. With spinel, i pyroxenes, magnetite, i

White

conspicuous F— Uneven Brittle

broken, columnar masses. In crystalline schists. With hornblende, vesuvianite, epidote, garnet, feldspars.

White

C— Basal, perfect

With quartz, feldspar, garnet.

T.

Grayish

F— Uneven

Brittle

vesuvianite, hornblende, pyroxene, magnetite.

Gray

C — Prismatic, py-

Not as heavy as cassiterite. Often

Yellowish white

ramidal, not

as fine hair-like inclusions.

Bro¥mish white

conspicuous F— Uneven Brittle

Widely distributed. With ite, chlorite, brookite.

B. Hiherals With Hok-Hetaluc Luster

Streak — Uncolored, white, or Ught gray

Name, Composition, and Referencea

Cryatallization Structure Oystala-C Massive— M

Luster Traosparency

Cassiterite

Dans. PuBODB

Tetragonal C— Thick prismatic; knee-shaped twins

H — Compact, reniform, botryoidal, rounded pebbles, often with internal, radial fibrous structure, tvood tin

Adamantine Resinous DuU Translucent to

opaque

Orthorhombic Vitreous Pink

C — Prismatic, rough. Dull Rose red

nearly square, often Translucent to Red violet

large and without opaque

—Columnar, fibrous, granular, dlssemi-

♦Olivihe

Orthorhombic

C — Prigmatic, thick

tabular H — Rounded, disseminated glassy grains; granular aggregates

Vitreous Brownish red

Dull Yellowish red

Translucent to

transparent

GARIfET, varieties

GrossTilaTtte R,"R,'"(SiOi), Pyrope R" =Ca,Fe,Mg SpessarltU R'" Al,Pe AlmaTtdiU

—Dodecahedrons, tetragonal trisoctahedrons, alone or in combination

—Granular, compact, lamellar, disseminated, sand

Vitreous Rose red

Transparent to Ruby red opaque Brownish red

Dark red

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a. PIHE, KED, OR SED VIOLET U COLOR

Hardneis over 6

Cleavage — G Fracture -F

Tenacity

Charactri8tics and

White C— Indistinct

Yellowish white F — Uneven Brownish white Brittle

Distinguished by high specific gravity. In veins cutting granite, gneiss; in alluvial deposits as stream tin. With quarts, wolframite, echeelite, arsenopyrite, tourmaline, fluorite.

C — Prismatic F— Uneven Brittle

Due to alteration, surface may be covered with scales of mica and, hence, is softer. In metamorphic rocks often as rounded or knotty projections. With cyanite, sillimanite, garnet, tourmaline.

White C— Pinacoidal

Brownish white F — Conchoidal Yellowish white Brittle

In basic igneous rocks — basalts, traps; crystalline limestones. With augite, magnetite, spinel, plagioclase, chromite, pyrope.

White

C— Dodeeahedra!

7J

Gray

distinct F — Conchoidal, u

Grossttlarile, in crystalline limestones and dolomites, with wollastonite, veauvianite, diopside, scapolite; pyrope, rounded grains, in serpentine; apessarlite, in granitic rocks, with topaz, tourmaline, quartz, orthoclase; almandile, with mica, staurolite, andalusite, cyanite; andradUe, with magnetite, epidote, feldspar, nephelite, leucite.

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B. mnERALS WITH HOIf-HETALLIC LUSTER

Streak

— Uncolored, white, or Ught gray

Name, Composition, and Referenoee

Crystallisation Structure Cryatals-C Massive

Luster Transparency

Color

QUARTZ, Phanerocrystalline

varieties

Hexagonal

C — Prismatic, horizon-

Vitreous Greasy

Red violet Rose red

SiO, Amethyst Rose quartz Aventurine

tally striated, com- H — Compact, eranular

Transparent to

opaque

Brick red Brownish red

Cryptocryatalline

varieties

Hexagonal

C— Never in crystals

Waxy Vitreous

Bright red Dark red

Corneiian

M— Banded, spotted.

Translucent to

Brownish red

Agaie Sardonyx Jaxper Heliolrove

compact

opaque

Clastic varieties Hexagonal

Sand Loose or strongly co Sandstone soUdated grains

QuarUUe fragments

and Kraiu. Daan. Psnuns

Dull Brownish red

Translucent to Purplish red opaque

TOURKALISE, variety

Hexagonal

C — Prismatic, often vertically striated, rarely with good terminations

H — Divergent, columnar, compact

variety C— Prismatic, tabular,

KumUt sometimes large

M — Cleavable, broad columnar

3 Is

Hexagonal

C — Rhombohedral, pyramidal, lenticular, highly modified

Vitreous Pink

Transparent to Rose red translucent Ruby red

Vitreous

Transparent

Vitreous Rose red

Transparent to translucent

:y

i. phik, red, or red violet in color

Cleavage - G Fracture -F

Tenacity

C Indistinct

F — Conchoidal, i BpicuouB

C — Indistinct F — Conchoidal, c

Specific Gravity

Characteric coachoidai Cracture and glassy luster. Amethyat, usually in cryatals, purple or blue violet; rose qtiartz, usually massive, pink to rose red; aventurine, massive and glistening, due to included scales; ferruginous quarls, colored by iron oxide.

Not as glassy as phancrocrystalliae varieties. Camelia-a, jasper, uniform in color; agate, sardonyx, banded; heliotrope, spotted. To distinguish, see references.

C — Indistinct F — Uneven Brittle to tough

Figment is usually ferruginous matter. Sand, loose, unconsolidated grains; sandelone, consolidated sand; quartzite, metamorphosed sandstone.

F — Conchoidal,

Spherical. triangular cross-section Often with local distributi color — red, green, colorless. Frequently as long, divergent, columnar masses imbedded in lepidolite.

of

—Prismatic, perfect; pinacoidal part-

F — Uneven, conchoidal Brittle

C — Prismatic, indis-

F — Conchoidal Brittle

Commonly in broad plates, due to distinct pinacoidal parting. Prism angle 93°. In granitic rocks. With tourmaline, tepidolite, beryl.

Distinguished from quartz and topaz by crystal form and cleavage. In pegmatites and metamorphic rocks. With quarts, topaz, beryl, amaionatone, chrysoberyl.

imiERALS WITH n05-H£TALLfC LUSTER Streak — Uncolored, white, or light gray

CrystBllizatioQ Structure Crystals -C Massive— M

Transparency

Tetragonal Adamantine

C — Prismatic, pyramidal, Vitreous

small, well developed Resinous

Hosea H — Irregular lumps. Transparent tc

Panons grains opaque

Brownish red

Dark red

Orthorhombic Vitreous Pink

C — Prismatic, vertically Transparent to Red

striated, highly opaque Red violet

modified M — Compact, granular,

rounded fragments

SPINEL, varieties

Balas R"(R"'0,), Ruby R"-Mg,Fe,Mn Rabicetie R'" — AI,Fe AlmaTidine

Vitreous Deep red

Splendent Rose red

Transparent to Orange red

translucent Bluish red

ISe. 338. 34

COROHDUH, varieties Ruby A1,0, Oriental

amethyst Common

Hexagonal

C — Prismatic, tabular,

pyramidal, rhombohedral

H — Compact, granular,

lamellar

Vitreous Pink

Transparent to Red translucent Red violet

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2. Piitk, K£D, Or Red Violet In Color

Hardness over 6

Cleavage - Fracture — Tenacity

, White

C— Indistinct F— Uneven Brittle

White

C— Basal, perfect, usually conspicu-

Brittle

C-Octahedral, iodis-

F— Conchoidal

Brittle

C — None. Nearly rectangular basal and rhombohedral partings, conspicuous; often striated

F — Conchoidal

Brittle to tough

Often in the more acid igneoiu rocks — granites, syenites; alluvial deposits, with gold, spinel, corundum, garnet. Hyacinth, dear and transparent.

Crystals usually developed on one end only. Massive varieties distinguished from quartz by great hardness, higher specific gravity, and basal cleavage. Color may fade on exposure. In veins and cavities in granitic rocks; alluvial deposits. With cassiterite, tourmaline, fluorite, beryl, scheelite, wolframite.

Balat spinel, rose red; ruby spinel, deep red; rubiceUe, yellow to orange red; almandine, bluish red. Usually in precious stone placers, with lircoa, garnet, magnetite; more rarely as contact mineral in crjrstalline limestones.

When massive often multi-colored -r-blue, green, gray, iiuin/, transparent, red; oriental amethyst, violet. In limestones, granites, , peridotites, alluvial deposits. With magnetite, hematite, nephelite, mica, spinel.

B. HinERALS WITH HOB-HETAIXIC LUSTER

Streak— Blue, green, brown, yellow, or black

Name, Composition, and

Crystallization Structure

Crystals -C Massive -M

Transparency

Glaoconitb reKSi,0,.H,0 T

Honoclinic 7 H — Sand, earthy, disseminated

Dull

Opaque

Dark green Light green

Monoclinic

Pearly

Grass green

ntel

C— Tabular, eix-sided.

Vitreous

Brownish

H.Mg.Ali.O,. 7

often bent and

DuU

twisted

Translucent to

Bladdsh green

M— Foliated, scaly.

opaque

granular, earthy

Monoclinic

Dull

Apple green

C — Hair-like, indistinct,

Vitreous

Light green

rare M— Earthy, crusts, stains

Opaque to translucent

Vinasite

Monoclinic

C — Prismatic, tabular — Reniform, globular, with radial fibrous structure; earthy

Vitreous Indigo blue

Dull Bluish green

Transparent to Blaoldsh opaque green

Covellito

Hexagonal

Indigo blue

C— Tabular, rare

Resinous

Blue black

CuS

M — Compact, granular,

Opaque

fii.

iS3 crusts

CluTBOColla H,CuSi0..H,0

Gamierite

Amorphous 7

M— Compact, reniform,

incrustations, seams, stains, earthy

Vitreous Greasy Dull Translucent to

opaque

Green Greenish

blue Blue

Amorphous 7 , H— Compact, reniform, earthy

Dull

Greasy Opaque

Pale green Apple green Emerald green

3. Greeit, Blue, Or Blue Violet In Color

Hardness 1 to 3

Cleavage — C Fracture -F Tenacity

Characteriatica and

Commonly as green sand. Resembles earthy chlorite. Disseminated in aandatones, limestonee, and marl.

conspicuouH F — Scaly, earthy Tough to brittle

—Earthy

Lamina are flexible but inelastic, with slightly soapy feel. Common in schists and serpentine. With magnetite, garnet, diopside, magnesite. Often as a scaly or dusty coating on other minerals, Pseudomorphous after garnet.

Common alteration product of nickel-arsenic minerals. With niccolite, chloanthite, calcite.

C — Clinopinacoidal F — Fibrous, earthy Sectile, thin laminse flexible

UsuaUy massive. Color and streak darken on exposure. In clay, peat, bones, shells. With limonite, pyrrhotite, pyrite.

F— Uneven Thin plates a

Characteristic blue color. With , chalcopyrite, bomite, chalcocite.

C— None

F — Conchoidal.

earthy Brittle

2 . Usually recognized by enamel-

2.2 like appearance, conchoidal fracture, and non-fibrous structure. When impure brownish or blackish. With copper minerals — malachite, aaurite, chalcopyrite.

2.3 Often as rounded, pea-shaped 2 . 8 masses with vamish-like surfaces and earthy interior. Frequently adheres to tongue. With olivine, serpentine, chromite,

B. HINBRALS WITH HOIT-HETALLIC LUSTER Streak— Blue, green, brown, yellow, or black

Cryetallwation

Name, Compositioa, and

Structure

References

Cryetale -C

Massive -M

Transparency

KrauB, Dana, 151. 534,

Mose

pi

Triclinie

C— Tabular, amall, rare M— Crusts, reniform, Btalactitic, powdery

Vitreous

Dull

Translucent

Deep blue Sky blue Greenish blue

K — Fine, crystalline,

warty crusts; rarely compact

Vitreous Transparent to translucent

Emerald green

Olivenite

17S, 504,

Orthorhombic

C— Prismatic, acioular

M— Reniform, fibrous,

with velvety surface;

earthy

Vitreous Transparent to

opaque

Light green Olive green Blackish gree

Streak— Bine, green, brown, yellow, or black

Atacamite

Orthorhombic

Vitreous

Bright green

C —Slender prismatic, usu

Adamantine

Emerald green

ally in confused

Transparent

Blackish green

fibrous aggregates

to nearly

M— Granular, compact,

opaque

Chrygocolla

Amorphous 7

Vitreous

Green

M— Compact, reniform,

Greasy

Greenish blue

HuSiO,.H,0

incrustations, seams,

Dull

Blue

stains, earthy Translucent to

opaque

Brochantite

Orthorhombic Vitreous Emerald g

C — Prismatic, acicular. Pearly Blackish

vertically striated Transparent to green M— -Reniform, fibrous, translucent

:y

3. Greeh, Blue, Or Blue Violet Dt Color

Cleavage — C Fracture -F Tenacity

Specific Gravity

CharacteristicB and Associates

C — Indistinct

F — Conchoidal Brittle

Disagreeable metallic taste. Oxidation product of copper sulphide minerals. With chalcopyrite, bornite, melanterite, pyrite, goslarite

Ab crusts on, or veinlets in chromite, niekeliferous magnetite, associated with serpentine.

Divergent, fibrous structure and velvety surface important. With copper minerals. Not as B malachite.

Hardness over 3

C — Brachypinacoidal F— Conchoidal

Brittle

With other copper minerals; also limonite, hematite. Not as common as malachite.

C — Brachypinacoidal

F — Uneven Brittle

Usually recognized by enamel- Lke appearance, conchoidal fracture, and non-fibrous structure. When impure brownish or blackish. With copper minerals — malachite, azurite, chalcopyrite.

Not as common as malachite. Secondary copper mineral. With malachite, azurite, cuprite, chalcopyrite, limonite.

:y

B. mifERALS WITH hou-icetallic luster

Streak — Blue, green, brown, Tellow, or black

Crystallization Structure Crystals Missive "-H

Luster Transparency

Azorite

Halachite

Pyromorpbite

Dioptase

Monoclinic Vitreous Azure blue

C — Short prismatic, tab- Dull Dark blue

ular, often in spher- Translucent to ical aggregates opaque

M — Fibrous; botryoidal, I with velvety or

,g radial structure; earthy, crusts

Monoclinic

C — Acicular, often in

groups or tuffs M — Fibrous; atalactitic, botryoidal, with smooth surface and internal banded or radial fibrous structure; velvety crusts, earthy

Hexagonal Greasy

C — Prismatic, thick tab- Adamantine

ular, rounded and Translucent

barrel-shaped opaque H — Globular, reniform, diaseminated, crusts

Silky Emerald

Adamantine green

Duli Grass green

Translucent to Dark green opaque

Dark green Emerald green

Yellowish

Hexagonal C— Prismatic, Mmall, highly modified M — Crystalline crusts

C — Dodecahedrons, rari H — Compaot, irregular

Vitreous Emerald Transparent to green

opaque Dark green

Vitreous Azure blue

Translucent to Violet opaque blue

Greenish blue

HORIfBLEIfDE (Amphibole) Silicate of Ca, Mg, Fe, Al, eti

Monoclinic

CLong prismatic, prism angle 124°; often with rhombohedrallike terminations

H — Bladed, fibrous, granular, compact

Vitreous Blackish

Silky green

Translucent to Dark green opaque

:y

3. Greer, Blue, Or Blue Violet Is Color

Cleavage Fracture -F

Tenacity

C — Domatic F — Conchoidal Brittle

Common alteration product of copper minerals. With malacliite, cuprite, native copper, chalcocite, chalcopyrite, bomite. Pseudomorphous after cuprite, tetrahedrite. Alters to mala-

C — Basal, pinacoidal F — Conchoidal, splintery Brittle

Very common alteration product of copper minerals. With azurite, cuprite, native copper, chalcocite, chalcopyrite, bomite. Pseudomorphous after cuprite, azurite, native copper. Surface may be almost black, due to the oxide, melaconite.

Yellow

C— None

Greenish yellow

F— Conchoidal Brittle

Alteration product of lead minerals. With galena, cerussite, mimetite, barite, limonite.

C — Rbombohedral F — Conchoidal, uiiev Brittle

In limestone, with quartz, and other copper minerals.

C— Dodecahedral, 2.4 Always blue and contains dia-distinct

seminated pyrite. Occurs as

F — Uneven ' contact mineral in crystalline

Brittle limestone.

Grayish green Grayish brown

Yellowish

—Prismatic, perfect, often conspicuous

Simple, pseudobexagonal crystals, and cleavage— 124° — important. In nearly all types of igneous rocks. With quartz, feldspar, pyroxene, chlorite, calcite.

B. Miherals With Hob-Metallic Ldster

Streak — Blue, green, brown, yeUoi

Crystallization

Structure

Luster Transparency

C — Short, prismatic, Silicate of Ca, Mg, Fe, Al, et. thick columnar;

prism angle 87° Moaea M — Compact, granular, KmuB, Dana, Paraona disseminated

Vitreous Sub metallic Translucent to opaque

Blackish

green Leek green

Turquois

Amorphous 7

Waxy

Sky blue

M— Reniform, stalaotitic,

Dull

Bluish green

disseminated, round-

Opaque to

Apple green

Glaucophanb

Monoclinic

Vitreous

Azure blue

C— Prismatic, indistinct

Pearly

Lavender blue

Silicate of Ca, Mg

Fe, Al

Na,

H — Columnar, fibrous

Translucent

Grayish blue

etc.

granular

2S5,

Chloritoid

Monoclinic

C— Tabular, six-sided

Vitreous Pearly

Dark green Grayish green

H,FeAI,SiO

M— Folia ted, scaly, platy; tan-and sheaf-like aggregates

opaque

Blackish green

Streak— Uncolored, iriiite, or Egt gray'

Adamantine Grayish

C— Rare Waxy green

M — -Wax-like crusts and Greasy Greenish

coatings; Btalactitic, Transparent to Grayish blue

dendritic translucent

Glauconite

Dull

Dark green

M— Sand, earthy, dis-

Opaque

Light green

FeKSi,0,.H,0?

1.

Orthorhombic

Greasy

Apple green

C— Indistinct

Pearly

Grayish green

H,Ali.O.,

M— Radiated fibrous,

Dull

Brownish

lamellar aggregates;

Translucent to

green

opaque

3. 6REEIT, BLUE, OR BLUE VIOLET m COLOR Hardness over 3

Cleavage Fracture -F Tenacity

Characteristics and

6. Pale green 6. Grayish green

C— Prismatic, perfect, conspicuous — 87° Brittle

Crystals, usually eight-sided, more rarely four sided; pseudotetragonal with prism angles of 87° and 93°. Cleavage less distinct than on hornblende. Common in basic eruptive rocks and crystalline limestones.

Secondary mineral, , common in thin veins, crusts, or coatings. With limonite, quartz, feldspar.

In metamorphic rocks. With mica, amphibole, pyroxenes, garnet, epidote, aoisite.

C — Basal, perfect,

conspicuous F— Scaly Brittle

Sometimes softer due to alteration. Recognized by micaceous structure, perfect cleavage, and hardness. In clay slates, mica schists. With corundum, garnet, chlorite, hornblende.

1. White, shiny 1.6 Gray, shiny

C— None

F — Conchoidal

Highly sec tile

C— Longitudinal F — Fibrous, unevi Laminffi flexible

Cuts like wax, yielding shiny surfaces; on exposure turns violet, brown, or black. With silver minerals — argentite, native silver; also limonite, calcite, barite.

Commonly as green sand. Resembles earthy chlorite. Disseminated in sandstones, limestones, and marls.

Soft and greasy like talc, but usually in radiating fibers. In schistose rocks. With cyanite, lazulite, topaz,

B. Huterals With Hov-Hetallic Luster

Streak— Uncolored. wHt, or light gray

Name, Compoeitioi

,and

Structure

CryrtalH-C

Hasaive-M

Luster Transparency

Color

Asbestos, variety H.Mgi,0.

Orthorhombie 7 M— Fibrous, coarse or flue; felted

Silky

Silky metalUo

Opaque

Light green Olive green

Kmua, Dans, Piinoiia

Ampkiboh Silicate of Ca, Mg, Fe, Al

etc.

Monoelinic ? H— Fibrous, coarse or fine; felted

Silky Opaque

Greenish

C — Scaly, hexagonal or

Une, rare M— Compact, friable, clay-like

Dull Pearly Opaque to translucent

Bluish Greenish

Vivianite

C— Prismatic, tabular H— Reniform, globular, with radial fibrous structure; earthy

Vitreous DuU

Translucent to opaque

Indigo blue Bluish green Blackish green

TALC, varieties

Foliated

H,Mgi.O„

Monoelinic

C— Thin tabular, indistinct M— Foliated, globular,

granular, compact, fibrous

Pearly Greasy

Opaque to transparent

Pale green Apple green Dark green

C— Tabular, six-sided, often bent, twisted

M— Foliated, scaly, granular, earthy

Pearly

Vitreous Dull

Translucent to opaque

Grass green BrownUh

green Blackish

green

Monoelinic

C— Hair-like, indistinct,

M— Earthy, crusts, tains

DuU Vitreous Opaque to trislucent

Apple green Light green

3. Greeh, Blue, Or Blue Violet Dt

Hardness 1 to 3

Hard-

Streak

Cleavage -C Fracture -F

Tenacity

Specific Gravity

Characteristics and

Associates

White

F— Fibrous Flexible

Delicate, fine, parallel, flexible fibers, easily separable, called short fibered asbealoa; compare below. In veins or seams in compact serpentine.

White

F— Fibrous Flexible

1,

Long fibered asbestos, parallel, flexible fibers. Compare above.

White Bluieh, white

Clay odor when breathed upon. Usually adheres to tongue and becomes plastic when moistened. Greasy feel. With quartz, feldspar, corundum, diaspore, topaz.

Bluish white Greenish white White

C — Cli nopinacoidal F— Fibrous, earthy Sectile, thin laminte flexilje

Usually massive. Color and streak dariien on exposure. In clay, peat, bones, shells. With limonite, pyrrhotite, pyrite.

White

Basal, conspicuous on fohated

F — Uneven Sectile, lamitiEe flexible

Greasy or soapy feel. Foliaied, easily separable, inelastic folia or

tUe, coarse to fine granular, more or less impure, H 1.5-2.5. With serpentine, dolomite, magnesite, actinolite.

White Greenish white

C— Basal, conspicuous, when foliated F— Scaly, earthy Tough to brittle

Lamins flexible but inelastic, with slightly soapy feel. Com-

With magnetite, magnesite, garnet, diopside. Often as scaly or dusty coating on other minerals. Pseudomorphous after garnet.

White Greenish white

C— None

F— Earthy

3,

Common alteration product ot nickel-arsenic minerals. With niccolite, ohloanthite, calcite.

milERALS WITH HOH-HETALLIC LUSTER

Streak — Uncolored, white, or light gray

Name, Composition, and

Crystallizatoi Structure CryetalB-C Massive— M

Traneparency

Dsaa. Poreons

Monoclinic C— Rare

M— Capillary, fibrous, Moe8~ stala otitic, concretionary, powder

Vitreous Green

Dull Yellowish

Transparent to green translucent

Cubic Vitreous

C — Cubes, alone or with Transparent to

octahedron translucent H — Granular, compact

Cubic

C— Cubes, often skeletal or hopper-shaped

M — Compact, cleavable, granular, fibrous, Btalactitic, crusts

Vitreous Transparent to opaque

Bluish

Blue Greenish

Bnicite

Hexagonal C— Broad tabular M— Foliated, fibrous, scaly

Pearly

Vitreous Transparent to translucent

Greenish white Green Bluish

Chrysocolla H,CuSiO..H,0

Amorphous 7 M— Compact, reniform, incrustations, seams,

Greasy

Dull

opaque

Green

Greenish

blue Blue

Garnierite

Amorphous 7 M— Compact, reniform, earthy

Dull

Greasy

Opaque

Pale green Apple green Emerald

green

Monoclinic Vitreous Grass green

C — Fine, acicular Silky Grayish

ttInterwoven fibrous Translucent to green

aggregates opaque

:y

3. Green, Blx7E, Or Blue Violet Iv Color

HardneBs 1 to 3

Cleavage -C Fracture — F Tenacity

Specific

White

C— Basal, not con-

F— Conchoidal,

earthy Brittle

White

C— Cubic

F— Conchoidal Brittle

2.B

White

C— Cubic, perfect, c

spicuous F— Conchoidal Brittle

White

C— Basal, perfect,

conspicuous Thin plates or sea flexible

White

QreeniEh white Bluish white

F— Conchoidal Brittle

C— None h

F— Conchoidal, earty Brittle

On exposure loses water and crumbles to powder. Sweet, astringent taste, somewhat metallic. Oxidation product of iron sulphide minerals — marcfisit e, pyrite, chalcopyrite, pyrrhotite.

Color due to impurities. Salty, bitter taste. May absorb moisture and become damp. Usually in salt deposits. With halite, kainite, carnallite.

Characteristic cubical cleavage and saline taste. May absorb moisture and become damp. With shale, gypsum, anhydrite, poly-

Distinguinhed from mica by nonelasticity and distinct pearly luster. Foliated talc is softer with greasy feel. With serpentine, limestone.

Usually recognized by enamel-like appearance, conchoidal fracture, and non-fibrous structure. When impure brownish or blackish. With copper minerals — - malachite, azurite, chalcopyrite; also limonite.

Often as rounded, pea-shaped masses, with varnish-like surfaces and earthy interior. May adhere to tongue. With olivine, serpentine, chromite, talc.

Masses of delicate, interwoven fibers — aelinoHte sexist. A pale grayish green, highly ferruginous variety (griiiiente, Fe.(Si05),) associated with quartz and magnetiteis teTmedmagnetiie-granerite schist.

B. UnERALS WITH ROIT-HETALLIC LtlSTER

' Strak

-tlncolored, white, or Ugl

Crys;:ilii2Htion

t gray

Nam;, Comriosition, and

fitnicture

Luster

Color

lU'Eorencea

Crystals -C

Transparency

Massive -M

Triclinic

Vitreous

Deep blue

C— Tabular, Bmall, rare

Dull

Sky blue

CuS0..5H,0

H — Crusta, reniform, atalactitic, fibrous,

Translucent

Greenish blue

powdery

Peariy

Greenish

Adamantine

agonal; twins.

Transparent to

trillings

translucent

la. 629.

M— Compact, lamellar

Vitreous

Greenish

C— Pseudohexagonal,

Pearly

Bluish

tabular, rare M— Stalactitic, mam miliary, surface smooth, internal structure fibrous; scaly aggre-

Translucent

white

gate

Monoclinio

Pearly

Green

C— Prismatic, tabular.

hexagonal or ortho-

Transparent to

rhombic outline,

translucent

often large or coarse

Ibiotite

scales

Pearly

Brownish

C— Tabular, hexagonal

Submetallio

green

or rhombohedral

Transparent to

Blackish

habit M— Plates, disseminated

opaque

green

scales

Orthorhombic

vitreo

Bluish

C— Tabular, prismatic.

Pearly

Greenish

crested divergent

Transparent to

groups, common

opaque

M— Compact, lamellar,

fibrous, oleavable.

reniform

3. GREGH, BLUE, OR BLUE VIOLET DT COLOR Hudneis 1 to 3

Cleavage — C Fracture -F Tenacity

Specific

. Gravity I

C — Indistinct

F — Conchoidal, earthy

Brittle

C — Basal, perfect F — Conchoidal

Rather sectile

DiEagreeable metallic taste. Oxidation product of copper sulphide miaerals. With chaloopyrite, bomite, melanterite,

pyrite, goslarite.

Soft and very heavy. Twins and triUings resemble those of aratconite. Usually with lead minerals, but sparingly. PeeudomorphouB after calcite, galena.

C — Basal, not conspic-

Strong clay odor when breathed upon. With bauxite, natrolite, limonite, corundum.

2.6 White 3. Gray

C- — Basal, perfect, con

spicuous Tough, lamins very

elastic

Especially characteristic of crystalline limestones, dolomites, schist. With pyroxenes, amphiboles, serpentine, apatite.

2.6 White 3. Grayish

—Basal, peri'ect, conspicuous

3ugh, laminie of fresh biotite very elastic

Easily recognized by i highly perfect cleavage, and elasticity. Important constituent of many igneous and metamorphic rocks — granite, syenite, gneiss.

C— Basal, prismatic,

conspicuous F — Uneven Brittle

Characterized by rather high specific gravity and cleavages. In metalliferous veins; pockets, lenticular masses in hmestone. With galena, sphalerite, chlorite, chalcopyrite; manganese and iron minerals.

B. Urerals With Honcetaluc Luster

Streak

— Uncolored, white, or gray

Name, Compositioa, s References

nd

Crystallieation Structure Crystals Massive -M

Luster Transparency

Color

AUopbane AliO,,6H,0

"St

Paraoni

Amorphous

M— Reniform, mammillary

, stalactitic, incniating

Vitreous Greasy

Sky blue Bluish green Deep green

CALCITE CaCO,

Hexagonal

M — Cleavable, granular, fibrous, compact

Vitreous

Dull

Transparent

to nearly opaque

Sky blue Deep blue Greenish

Tetragonal

C— Square, thin tabular; more rarely pyramidal

M— Coarse, fine grained

Greasy

Transparent to translucent

Light green Olive green

Streak

— Uncolored, white, or light gray

C— Pseudohexagonal, tabular, rare

M — Stalactitic, maramillary, surface smooth, internal structure fibrous; scaly aggregates

Vitreous Pearly

Greenish Bluish white

Ahhydrite

Orthorhombic

C— Thick tabular, prismatic, rare

M— Granular, compact, fibrous, lamellar, cleavable, reniform

Vitreous Pearly

Translucent to opaque

Bluish Grayish blue

Blue

Orthorhombic

C— Tabular, prismatic,

common; pyramidal M— Compact, cleavable,

fibrous, granular,

reniform

Vitreous Pearly

Transparent to

Sky blue

Blue

Greenish

3. green. blue, or blue violet m color

HardnesB 1 to 3

Cleavage - Fracture — Tenacity

Specific Gravity

F — Conchoidal, earthy 1 9 Structure resemblea opal. In fie- Brittle sure and cavities with copper

and iron minerals.

C — Rhombohedral perfect, conspicuous F — Conchoidal Brittle

Rhombohedral cleavage generally characteristic. Geavagea often

show Btriations.

C — Pyramidal, india-

P — Conchoidal, uneven - Brittle

Square plates, sometimes with forms of the third order. With lead minerals—galena, pyromoi phite, vanadinite.

Hardness 3 to 6

C — Basal, not conspic- Tough

Strong clay odor when breathed upon. With bauxite, natrolite, limonite, corundum.

C — Pinacoidal, perfect, 3 directions at 90° F — Conchoidal Brittle

Pseudocubical cleavage, sometimes noted. Granular varieties resemble marble. Not as heavy as celestite or barite. In limestone, shale. With halite, gypsum.

C — Basal, prismatic,

conspicuous F — Uneven Brittle

Heavier than calcite, anhydrite; lighter than barite. In hmestones, dolomites, shales. With sulphur, gypsum, aragonite, halite, galena, sphalerite.

:y

B. miTERALS WITH VOU-ICETALLIC LUSTER

Streak

Name, CompoBition, and

CrjTBtaUization Structure Crystals -C Massive -M

Luster Transparency

Color

KraiH, Dmm 13S. 624.

- Orthorhombic C — Tabular, prismatic, crested divergent groups, common Moms M— Compact, lamellar, pL fibrous, cleavable, 3JS reniform

Vitreous Pearly

translucent

Bluish Greenish

'AMGLESITE PbSO.

Orthorhombic

C— Prismatic, tabular,

pyramidal H~Compact, granular,

nodular

Adamantine Greasy

Transparent to translucent

Blue

Chrysocolla HAiSiO..H,0

Amorphous T

H— Compact, reniform,

incrustations, seams.

Vitreous

Greasy Dull

Blue Bluish

green

stains, earthy Translucent to Green

opaque

SERPEHTiHE H,Mgi,0,

Orthorhombic 7 Greasy Light green

CUnknowQ Waxy Olive green

H — Compact, columnar. Translucent to Yellowiah]

fibrous, lamellar, opaque . green

granular Blackish green

Orthorhombic

Vitreous

Green

C — Capillary, small

Bluish

H— Cruste, globular or

Blue

radial fibrous structure

3. Greek, Blue, Or Blde Violet In Color

Cleavage - Fracture — Tenacity

Specific Gravity

C — Basal, priHmatic,

conapicuoUB F— Uneven Brittle

Characterized by rather high specific gravity and cleavages.

metalliferous lenticular i With gale

pockets, tea in limestone. sphalerite, cbal-

C — Basal, prismatic F — Conchoidal BritUe

Luster and very high specific gravity important. Oxidation product of lead minerals. Usually in cracks and cavities. With galen

White

Greenish white Bluish white .

F — Conchoidal, splin Brittle

Usually recognized by enamel-like appearance, conchoidal fracture, and non-fibrous structure. When impure brownish or blackish. With copper mineralsmalachite, azurite, chalcopyrite; also limonite.

Smooth and greasy feel. Often spotted, clouded, and multicolored. Sometimes crossed by seams of asbestos (chrysotile). Verd'antique, massive, green and mixed with calcite, dolomite, or magnesite; takes an excellent polish. With magnesite, chromite, gamierite, pyrope, plati-

C — Pinacoidal, domatic F— Conchoidal, uneven,

fibrous Brittle

Secondary mineral occurring on surfaces of rocks or minerals, as crystalline crusts with pronounced radial, fibrous structure.

B. Wherals With Roh-Hetallic Luster

Streak— Uncolored, bite, oi tight gnj

Cryatallizatioi Btmcture Crystals -C Massive— M

ARAGOHITE CaCO,

Kraiu, Dana,

lie. 361, Scorodlte FeAs0..2H,0

Orthorhombic

C— Cliiselor spearshaped; pseudohexagooal prisms; radial columnar, acicular

Vitreous Transparent to translucent

Greenish Bluish

Violet

MOM8 aggregates ptL M— Stalactitic, renitorm, 332 cruata, oolitic

Orthorhombic Vitreous Pale green

C— Priamatic, pyramidal Greasy Bluish green

drusy Translucent Blackish

H — Botryoidai, fibrous, green

earthy, crusts Blue

STROHTIAHITE SrCO,

Orthorhombic

C — Spear-shaped, columnar, acicular, often in diveient groups

H — Granular, compact, botryoidai, fibrous

Vitreous Light green

Transparent to Apple green

translucent

Pyrohorphite

Hexagonal

C — Prismatic, thick tabular, rounded and barrei-shaped; acicular

M — Globular, reniform, disseminated, crusts

Greasy Dark green

Adamantine Emerald green

Translucent to Yellowish

opaque green

Hexagonal Vitreous

C — Rhombohedral, rare Translucent H — leavable, granular,

compact, botryoidai,

Cap,

C-Cubes, alone or modified, well developed, common; penetration twins

K — Cleavable, granular, fibrous

Vitreous Greenish

Transparent to Bluish green

nearly Blue violet

opaque

:y

3. Greev, Blue, Or Blue Violet Iif Color

Cleavage — C Fracture '"F Tenacity

C— Pinacoidal, pris-

Twins common, often paeudohexagonal— prism and striated base. In cracks knd cavities with ore deposits; deposition from hot Bprings; in shells. With gypsum, celestite, sulphur, Biderit, zeo-

White Grayieh Greenish white

C— Imperfect

F— Uneven, conohoidai

Brittle

White

C— Priamatic, indistinct F— Uneven Brittle

White

Yellowish white

C— None Brittle

With arsenopyrite, enargite, limonite

, pyrite.

Similar to aragonite. Divergent columnar structure, and higher specific gravity characteristic. In ore deposits; independent beds. With galena, barite, calcite.

Common alteration product of lead minerals. With galena, cemssite, mimetite, barite, limonite.

C — Rhombohedral,perfect

, conspicuous F— Uneven Brittle

C — Octahedral, perfect,

conspicuous Brittle

May turn brown or black on exposure, due to MnO,. With ore deposits. With galena, sphalerite, pyrite, alabandite, psiiomelane, silver minerals.

May show fluorescence. Easily recognized by crystal form, octahedral cleavage, and hardness. Common gangue of metallic ores — galena, sphalerite, cassiterite; also with calcite, barite.

:y

B. Miderals With Itoh-Hetallic Luster

Streak

— Dncolored, white, or light gray

Crystallization

Name, Compoaition, and

Structure

Luster

Color

Referencea

Crystals

Transparency

Massive '-M

Triolinic

Vitreous

Sky blue

C— Long, bladed, with-

Translucent to

Greenish blue

out good terminations; sometimes curved and radially grouped

transparent

Bluish white

Kraus,

Dana

Parson

M— Coarsely bladed, co-

3B2

lumnar, fibrous

Tetragonal

C— Pyramidal, smalt.

Adamantine Greasy

Greenish

more rarely tabular

M— Drusy cruBts, reniform

, granular, dis-

Transparent to translucent

Apatite

Hexagoual

Greasy

Grass green

C— Prismatic, thick, tab-

Vitreous

Brownish

ular, common, some-

Translucent to

green

times large with

opaque

Bluish green

rounded edges

Blue violet

MCompact, fibrous,

nodular, reniforra

Orthorhombic

Vitreous

Pale blue

C — Thin tabular, pyram-

Bluish green

idal, hemimorphic, highly modified M— €ompact, globular, stalactitic, fibrous.

opaque

Pale green

granular

Smithsomite

Hexagonal

Vitreous

Green

C— Small, usually as

Dull

Grayish green

druses or crusts H— Botryoidal, stalactitic, granular, fibrous.

Translucent

Greenish blue Blue

compact

Cubic

Vitreous

Azure blue

Translucent to

Violet blue

NaS„-

H — Compact, irregular

opaque

Greenish blue

grains

3. Oreeit, Blue, Or Blue Violbt Ik Color

Hudaesa 3 to 6

Cleavage -C Fracture -F Tenacity

C— PinacoidaJ, perfect, 3 5

C — Pyra.midal F— <onchoidal, ii Brittle

C — Basal, imperfect F — Conchoidal, uneven Brittle

Color irregularly distributed, frequently with lighter longitudinal margins. Hardness varies with direction, 4-5 parallel to long direction, 6-7 at right angles thereto. In gneiss, mica schist. With Btaurolite, garnet, corun-

Small, well developed octahedral' like crystals, usually on quartz; when massive high specific gravity important. With cassiterite, wolframite, fluorite, apatite, molybdenite, topaz.

Crystals may be vertically striated and have fused appearance. Color often unevenly distributed — brownish spots. In crystalline limestones; metalliferous ore deposits; igneous rocks. With quartz, cassiterite, fluorite, wolframite.

White

C — Prismatic

Crystals often in sheaf-Kke groups

F — Uneven, conchoidal Brittle

or druses in cavities. In limestone. With sphalerite, galena,

White

With zinc minerals, especially

Gray

not often observed F— Uneven, splintery Brittle

sphalerite, hemimorphite.

White

C— Dodecahedral, im-

Always blue and contains dis-

Bluish white

perfect FUneven

contact mineral in crystalline

Brittle

limestone.

B. UniERALS WITH ITOn-HETALLIC LUSTER

Streak

— Uncokired, white, or light gray

Name, Composition, and

Structure

Luster

Color

References

Crystals -C Massive -M

Transparency

Datolile

Moaoclinic

Vitreous

Pale green

CPrismatic, pyramidal.

Greasy

Olive green

tabular, highly modified M— Compact, fibrous, granular, botryoidal

Dull

Transparent to opaque

Kraua, Dana,

Monoclinic

Vitreous

Lazulite

Aaure blue

C— Acute pyramidal, tab-

Translucent to

Sky blue

ular M— Compact, granular

opaque

Monoclinic

Vitreous

Green

C— Wedge-or envelope-

Greasy

shaped when dia-prismatic

when attached

Transparent to translucent

green

M— Compact, lamellar

vitreous"

Sodalile

Cubic""" '

lavender blue

C— Dodecahedrons

Greasy

Sky blue

M— Compact, dissemi-

Transparent to

Dark blue

nated grains, nodular

translucent

Greenish

Cancrinite

Hexagonal

Vitreous

Green

C— Prismatic, rare

Pearly

Grayish blue

H— Compact, lamellar,

Greasy

Blue

3i.0„

columnar, dissemi-

Transparent to

nated

translucent

Hejcagonal

Greasy

Grayish green

C— Short prismatic, tab-

Vitreous

Brownish

ular

Transparent to

green

H-Compact, dissemiopaque

Grayish blue

2:w, 40B,

nated grains

Tetragonal

Vitreous

Grayish green

C— Thick prismatic,

Greasy

Bluish

/ nXa.Ali.O„C!

coaree, often large

n.Ca.Al,Si,0„

M— Compact, granular, fibrous, columnar

opaque

3. GREEH, BLDE, OR BLUE VIOUIT IH COLOR Hordiwfls 3 to 6

Cleavage Fracture — F Tenacity

B. Whit* 5.6 Grayish

C — Indistiftct F— Uneven Brittle

—Prismatic, conspicuous parting often

Crystals glaaay and usually well developed. Compact masses often with brownish, yellowish, reddish streaks' and spots. In cracks and cavities in basic igneous rocks. With calcite, prehnite, native copper, magnetite, zeolites.

Pyramidal crystals are pseudotetragonal and well developed. Disseminated in quartz, clay at slate. With corundum, cyanite,

with feldspars, pyroxenes, amphibolee, chlortt, scapolite, zircon.

C— Dodecahedral

F — Conchoidal, uneven

Brittle

C — Prismatic, perfect F — Uneven Brittle

Commonly massive and blue in

color Recognized by associates

nepheLte cancnnite, leucite,

feldspar zircon not with quartz.

Associates important — nephehte, sodalite, biotite, feldspar, titanite.

C — Prismatic

F — Conchoidal Brittle

Greasy luster and associates important. With feldspar, cancrinite, biotite, sodalite, zircon, leucite; not with quartz.

Crystals may appear as though fused. Typical contact mineral. In metamorphic rocks, especially granular limestones. With pyroxenes, garnet, mica, amphiboles, wollastonite.

B. Minerals With Hoh-Hetallic Luster

StreokDncotOFed, white, or light graj

CryBtallization Structure Crystals -C Massive — M

Luster Transparency

Actinolite

Vitreous

Light green

C— Bladed, without ter-

SUky

Grayish green

minations

Transparent to

Dark green

Moses

H — Columnar, fibrous,

opaque

KmuE, Dana

Tl

often divergent;

granular, compact

Vitreous

Blackish

C — Long prismatic.

Silky

green

Silicate of Ca, Mg,

Fe, Al, etc.

prism angle 124°; often with rhombohedral-like terminations H— Bladed, fibrous, granular, compact

opaque

Dark green

Enstatite

Orthorhombic

Vitreous

Grayish green

C— Prismatic, rare

Pearly

Brownish

M— Fibrous, lamellar.

Translucent to

green

columnar, compact

opaque

Olive green

Brohzite

Orthorhombic

Broniy

Grayish green

C— Prismatic, rare

saky

Brownish

HFibrous, lamellar,

TranBlucent to

green

opaque

Olive green

Hypersthene

Orthorhombic

Pearly

Brownish

1 Diopside I

—Prismatic, tabular. Metalloid al green

rare Translucent to Blackish green

Granular, foliated, opaque cleavable aggregates

Monoclinic Vitreous Pale green

C — Prismatic, thick co- Dull Bright green

lumnar, prism Transparent to Dark green

angle 87° opaque H — Compact, granular,

columnar, lamellar

' 243. 388. 386

I augite"

I Silicate or Ca, Mg, Fe, Al,

Monoclinic Vitreous

C — Short prismatic, thick Submetallio

columnar, prism Translucent to angle 87° opaque

M — Compact, granular, disseminated

Blackish green Leek green

3. GREEK. BLUE, OR BLUE VIOLET m COLOR Hardness 3 to 6

Cleavage Fracture — F Tenacity

CPriBmatic, often conspicuous, 124° Brittle

2.9 In talc and chlorite echists. With 3.2 serpentine, epidote, calcite.

Nephrite and jade are compact J varieties.

Gray C — Prismatic, often

Greenish gray conspicuous, 124°

Brownish gray Brittle

2.9 Simple, pseudohexagonal crystals, 3,3 and cleavage — 124° — important.

Common in many types of rocks.

With quartz, feldspar, pyroxene,

chlorite, calcite.

White

C— Prismatic, pinacoid-

Often softer due to alteration to

Greenish white

al

serpentine. Commonly in basic

Grayish

F — Uneven Brittle

igneous rocks. With olivine, serpentine, chondrodite, talc.

White

C— Prismatic, pinacoid-

Cleavage surfaces often fibrous or

Grayish

al, often conspic-

F — Uneven

Brittle

lamellar, irregular or wavy, with distinct broniy luster. Darker than enstatite. In basic igneous rocks.

G.

White

C— Brachypinacoidal ,

Copper red iridescence often noted.

Gray

conspicuous

Brownish

gray

F— Uneven Brittle

In basic igneous rocks. With feldspar (labradorite), olivine, hornblende, pyrrhotite, magnetite.

White

C— Prismatic; conspic-

Crystals prismatic and pseudo-

Gray

uous basal parting F— Uneven Brittle

tetragonal with distinct basal parting. May have colorless and dart green zones. In crystalline Umestones and schists. With vesuvianite, garnet, scapolite, spinel, apatite.

White

C— Prismatic, perfect.

Crystals usually eight-sided, more

e.

Gray

conspicuous-87'

rarely tour-sided; pseudotetrago-

Greenish

gray

Brittle

nal with prism angles of 87° and 93°. Cleavage less distinct than on hornblende. In basic igneous

B. HinERALS WITH HON-HETALLIC LUSTER

Streak — Uncolored, white, or light gray

Crystallization

Structure Luster

Crystals — C Transparency

Massive

Chlobastroutb

C— Unknown

Vitreous

Green

M — -Rounded grains,

Silky

Bluish green

?

Hoees

pebbles

Translucent

Dark green

Kraus, Dana,

Paraons

Hexagonal

Vitreous

Apple green

C— Prismatic

Greasy

Yellowish

M— Compact, granular,

Translucent to

green

disseminated grains

opaque

Opal

Amorphous

Vitreous

Green

KRenitorm, botry-

Greasy

Bluish green

SiO,.icH,0

oidal, compact

Translucent to

Blue

opaque

Turquois

Amorphous 7

Waxy

Sky blue

M— Reniform, stalactitic,

Dull

Bluiah

Opaque to

green

rounded pebbles

Apple green

♦Amblygonite

Triclinic

Pearly

Greenish

C— Rare

Vitreous

Bluish

M — Cleavable, columnar, compact

Translucent

Streak — Dncolored, white, or light gray

I mCROCLIHE, variety Triclinic Vitreous Bright green

I Amazonelone C — Prismatic, thick tabu- Pearly Bluish green

I KAlSljOj lar, twins Translucent to

I [ H — Cleavable, granular, transparent

compact, dissemi- ; 204. 373, 380 nated

Labradorite Triclinic

Vitreous

Grayish green

C— Thin tabular, often

Pearly

Greenish

Silicate of Ca,Na,Al with rhombic cross-

Translucent

to nearly

M— Compact, cleavable.

opaque

3. Green, Blue, Or Blue Violet Is Color

Hardness 3 to 6

Cleavage -C Fracture -F Tenacity

Rounded grains in basic, amygdaloidal rocks, also as pebbles. Color unevenly distributed. May show radial, fibrous structure and chatoyancy.

C— Basal F — Uneven Brittle

Characterized by associates — franklinit {black), incite (red), rhodonite (flesh red), calcite.

F — Concboidal, BpicuouB

Structure and fracture characteristic. Precious opal, play of colors. Id veins, cavities, and masses of irregular outline.

C— Basal, perfect, conspicuous; macropinacoidal, domatic

F — Uneven, conchoidal

Brittle

Secondary mineral, commonly in thin veins, crusts, or coatings. With quartz, feldspar, kaohn, limonite.

Usually in cleavable masses with perfect cleavage in one direction. With lepidolite, rubellite, topaz, wavellite, petalite.

HardneBS over 6

Basal, brachypinacoidal, conspicuous, 90° SC

F— Uneven

Brittle

Slightly inclined cleavages; may show twinning striations on basal pinaooid. With quartz, other feldspars, mica, hornblende, topaz, phenacit.

C — Basal, brachypinaooidal, conspic-

FUneven, concboidal Brittle

Often with play of color — yellow, green blue, red. Inclined cleavages are striated. In basic igneous rocks. With pyroxenes, amphiboles.

HDIERALS WITH ROIf-HETALLIC LUSTER Streak— Uncolored, white, or Ht gray

CrystaUiKatioQ Structure Crystals -C Haaidve— M

Luster Transparency

Silicate of Mg, Pe, Ca, Al, Na

Monolinic

C — Prismatic, iadietinct H — Columnar, fibrous, granular

Vitreous Aeure blue

Pearly Lavender blue

Translucent Grayish blue

Orthorhombic Vitreous Grayish green

C — Prismatic, deeply Pearly Apple green

striated, bent, with- Translucent to ! out good terminations opaque „ H — Columnar, broad bladed, fibrous

Prehnite

Orthorhombic Vitreous Light green

C — Tabular, prismatic; Waxy Apple green

curved, sheaf-like Transparent to Yellowish

groups translucent green

M — Botryoidal, stalactitic

, radial fibrous

Uonoclinic

C — Long prismatic, f often etched

Vitreous Yellowish

Transparent to green

translucent Emerald green

Orthorhombic Vitreous Grayish green

C — Long, thin needle- Silky Pale olive

like Transparent to green

M — Fibrous, columnar, translucent

radiating

R/'R."'B,(SiOJ, R" -CaJ'e,Mn,Mg R"'=AI,Fe

Triclinic Vitreous Green

C— Broad tabular, with Transparent to Yellowish

sharp edg translucent green

M — Lamellar, granular Plum blue

:y

3. OREEH, BLUE, OR BLUE VIOLET Df COLOR

Cleavage Fracture Tenacity

CharacteriBtica and Aeaociates

In metamorphic rocka. With mica, amphiboles, pyroxenes, garnet, epidote, zoisite.

White

C— Pinacoidal, perfect,

conspicuous F— Uneven Brittle

broken, columnar masses. In blende, cyanite, epidote, garnet.

veBuviaaite, feldspar.

C — Basal, indistinct

F.Uneven

Brittle

Massive varieties usually have rough, crystalline surfaces and internal, radial fibrous structure. Color fades on exposure. In veins and cavities in basic igneous rocks. With pectolite, datolite, epidote, native copper, zeo-

C — Pinacoidal F — Uneven Brittle

Small, transparent oryetak, resembling green diopside. In cavities in granitic rocks. With beryl,

monazite, rutile.

Crystals often bent, striated, edges rounded, without good terminations, and often interlaced. In metamorphic rocksgneiss, mica schist. With andatusite, zircon, garnet, iolite.

C — Pinacoidal 3.3 Crystals sharp wedge-shaped,

' F — Conchoidal glassy, and frequently coated and

Brittle intergrown with green chlorite.

With quartz, adularia, albite,

hornblende.

:y

B. HIHERALS WITH IfOIf-HETALLIC LUSTER Streak — Dncolored, white, or Ugbt gray

CryetallizatioD Structure CrystaU-C Massive —M

Transparency

Duia, Panofu

MoDoclinic Vitreous Blackish green

C — Prismatic, elongated Transparent to YeUowish

and deeply striated opaque green

parallel to b axis; Brownish

usually tenninated green

oa one end only Pea green H — Columnar, fibrous, parallel and divergent; granular

I'Diaspore AIO.OH

Orthorhombic Vitreous Greenish

C— Broad columnar, tab- Pearly Violet blue

ular, rare Transparent to

H — Scaly, confused translucent

fibrous or bladed aggregates

Ohloritoid HJ-eAliO,

Monoclinic Vitreous Dark green

C — Tabular, siz-sided Pearly Grayish green

M — Foliated, scaly, platy; Translucent to Blackish

fan-and sheaf-like opaque green

aggregates

Ardaldsite

Triclinic Vitreous Sky blue

C — Long bladed, without Translucent to Greenish blur good terminations; transparent Bluish white

sometimes curved and radially grouped M — Coarsely bladed, columnar, fibrous

Orthorhombic Vitreous Pale green

C — Prismatic, rough, Dull Olive green

nearly square, often Translucent to

large and without opaque

terminations H — Columnar, fibrous,

granular, dissemi-

:y

3. GREEK, BLUE, OR BLUE VIOLET UT COLOR Hardness over 6

Cleavage Fracture — F Tenacity

Speeifle Gravity

White Grayish

Crystale are often dark or blackish green, massive aggregates lighter colored. With quart*, feldspar, garnet, hornblende, pyroxene, magnetite, native copper, zeo-

C — Pinacoidal, c

apicuoos F — Conchoidal Very brittle

With corundum, emry, dolomite, margarite, chlorite, magnetite.*

White C— Basal, perfect, c

Greenish white spicuous

Grayish F — Scaly

Brittle

C — Pinacoidal, perfect,

conspicuous Brittle

Sometimes softer, due to alteration. Easily recognized by micaceous structure, perfect cleavage, and hardness. In clay slates, mica schists. With chlorite, bomblende, garnet, corundum.

Color irregularly distributed, frequently with lighter longitudinal margins. Hardness varies with direction, 4-6 parallel to long direction, 6-7 at right angles thereto. In gneiss, mica schist. With ataurolite, corundum.

C — Prismatic F — Uneven Brittle

Due to alteration, surfaces may be covered with scales of mica, hence, softer. In metamorphic rocks, often as rounded or knotty projections. With cyanite, sillimanite, garnet, tourmaline.

B. HinERALS WITB nOH-HETALUC LUSTER Streak — Uncotored, white, or light gray

Crystallizatioa

Name, Composition, and

Structure

Luster

Col r

References

CrystalB-C Massive -M

Transparency

Vesdyiahite

Tetragonal

Vitreous

Green

C — Short prismatic

Greasy

Brownish

H — Compact, granular.

Translucent to

green

Mows

aggregates with par-opaque

Bluish

Kraun. Dsas,

allel or divergent

striations

Orthorhombio

Vitreous

Grass green

C— Prismatic, thick tabu-

Transparent to

Olive green

lar

Yellowish

M— Romided, dissemigreen

nated glassy grains;

GARRET, varieties

Cubic

Vitreous

Pale green

Gros$iilarUe

C— Dodecahedrons, te-

Transparent to

Grass green

tragonal trisoctaheopaque

Emerald green

R"'-Al,Fe,Cr AndradUe

drone, alone or in

R"-Ca,Fe,Mg

combination M — Granular, compact, lamellar, disseminated grains, sand

Hexagonal

Vitreous

Green

varieties

C— Prismatic, horizon-

Greasy

Greenish blue

SiO, ChloriHc

tally striated

Transparent to

Blue

Cat's eye

H — Compact, granular

opaque

Blue violet

Amethyst

Cryptooryatalline

Hexagonal

Waxy

Light green

varieties

C — Never in crystals

Vitreous

Dark green

Chakedony

M— Nodular, spotted.

Translucent to

Grayish blue

Chrysoprase

concretionary, stal-opaque

Greenish blue

Prase

actitic, compact

Plasma

Boracite

Psendocubic

Vitreous

Greenish

C— Tetrahedral, cubical.

Transparent to

Bluish

Mg,Cl.B..O„

M— Compact, nodular.

opaque

fine fibrous

Uooommon ijolor.

Diai.zodBjGoogle

3. Oreeh. Blue. Or Blue Violet Ih Color

Cleavage Fracture - V Tenacity

Gravity

Characteriatics and Associates

C — Basal, prismatic,

indistiDct F— Uneven Brittle

In crystalline limestone, gneiss, schists. With garnet, tourmaline, chondrodite, wollastonite, epidote, pyroxene.

White C— Pinacoidal

Yellowish white F — Conchoidal Brittle

In basic rocks — basalts, traps; crystalline limestones. With augite, magnetite, spinel, plagioclase, chromite, pyrope.

C — Dodecahedral, i ally indistinct

F— Conchoidal, une Brittle

Groaaularile, in crystalline limestones and dolomites, with wollastonite, vesuvianite, diopside, Bcapolite; uvarovite, in serpentine, with chromite, or in crystalline limestones; andradite, with feldspar, nephelite, leucite, epidote, magnetite.

White

C— Indistinct F— Conchoidal, conspicuous Brittle

Characteristic conchoidal fracture and glassy luster. Chloritic

rite; cat's eye, opalescent, due to included fibers of asbestos; atne- Ihyst, purple or blue violet, usually

in crystals.

White

C— Indistinct

F— Conchoidal, conspicuous

Brittle to tough

Not as glassy as phanerocrystalline varieties. Chalcedony, chryso- 'prase, prate, plasma, uniform in color; heliotrope, spotted. To

White

C— None

F — Uneven, conchoicompact

masses resemble fine

dal

grained marble. With gypsum.

Brittle

anhydrite, halite, camallite.

B. HIHERALS WITH IfOH-BIETALUC LUSTER

Streak

— Uncolored, white, or light gray

Crystallisation

Name, Composition, and

Structure

Luster

Color

References

Crystals Massive 'M

Transparency

Orthorhombic

Vitreous

Light blue

C — Short prismatic,

Dull

Violet blue

Transparent to

Smoky blue

H — Compact.dissemitranslucent

Greenish blue

nated, granular

Knua. DanA, Psro<

23B, 407, 384

Tourhalihe

Hexagonal

Vitreous

Green

C— Prismatic, vertieaUy

Transparent to

Blue

striated; terminated

M'-Na,K,Li,Mg,Fe

with brolfen or rhombohedral-like surfacea

1B3. M7, 409

Hexagonal

BERYL, varietiee

Vitreous

Pale green

Emerald

C— Long prismatic, often

Transparent to

Emerald green

verticaDy striated,

translucent

Bluish green

Common

large M— Columnar, granular, compact, rounded pebbles

Sky blue

Cubic

Vitreous

Grass greeu

C— Octahedral, usually

Dull

Dark green

well developed

Translucent to

Grayish green

R"=Mg,Fe GahniU

M— Compact, granular,

opaque

Light blue

Zn.Mn Blue spinel

disseminated grains

Orthorhombic Vitreous Pale blue

C — Prismatic, vertically Transparent to Bluish green

striated, highly opaque Light green

modified H — Compact, granular,

rolled fragments

:y

3. Greev, Blub, Or Blue Violet In Color

Cleavage -C Fracture -F

Tenacity

Gravity

C — Pinacoidal, sometimes conspicuous

F — Conehoidai, v

Brittle

C — Indistinct F — Conehoidai, u Brittle

When fresh, glassy and hard, resembling blue quartz; usually altered, then dull and softer. Transparent varieties may show pronounced dichroiam macroscopically. With quartz, feldspar, hornblende, silUmanite, andalusite.

Spherical triangular crosH-section. With zonal distribution ot color — green, red, colorless. In igneous and metamorphic rocks. With lepidolite, feldspar, quartz, biotite.

Crsrstals usually simple — prism and base. Emerald, transparent and emerald green; oquamaHne, transparent, bluish to sea green or yellowish green. In granitic rocks, mica schists, clay slates, placers. With quartz, feldspar, mica, topaz, tourmaline, cassiterite, chrysoberyl, garnet.

White

C— Octahedral,

indis-

Commonly as contact mineral in

Grayish

tinct F— Conehoidai Brittle

granularlimestonea; in more basic igneous rocks; rounded grains in placers. With calcite, chondrodite, serpentine, brucite, corundum, graphite, pyroxenes.

C — Basal, usually c

spicuous F — Conehoidai, une' Brittle

Crystals usually developed on one end only. Color may fade on exposure. In veins and cavities in granitic rocks; alluvial deposits. With cassiterite, tourmaline, apatite, beryl, scheelite, wolframite.

:y

B. MMEHALS WITH HOIT-METALLIC LUSTER Strettk~-tTiicolored, white, or light gray

CrTBtalliiatioD Structure CryBtftla-C Massive - M

Transparency

Cbrysoberyl, varieties

Ordinary Alexaitdriie

Orthorhombic Vitreous Light green

C— Tabular; heart-shap- Greasy Yellowish

ed, paeudohexagonal Transparent to green

twins translucent Emerald

H — Compact; loose,

' rounded grains i

CORUHDUH, varieties Sapphire AljO, Oriental emerald

Oriental amethyst Cojnmon

Hexagonal

C — Prismatic, tabular, pyramidal, rhomboliedral; rough or rounded barrelshaped H — Compact, granular, lamellar

Vitreous Green.

Transparent to Blue opaque Blue violet

:y

3. Oreeh, Blue, Or Blue Violet Ih Color

Cleavage

Fracture— F Tenacity

Characteristics and AsBociates

Cryatala disaeminated as plates with feather-Uke or radial striations. AlexaTtdriie, red in transmitted light; cat's eye, opaleecent. In mica schiat, Jeisa, granite; also in placers. With beryl, garnet, tourmaline, sillimanite.

C — None; nearly rectangular basal and rhombohedral parting, conspicuous; often Htriated

F — Conchoidal

Brittle to tough

When maBaive, often multi-colored — red, gray,, yellow. Sapphire, transparent, blue; oriental emerald, green, transparent; oriental amethyst, violet. In limestone, granite, ayenite, schist, peridotite; placers. With magnetite, nephelite, mica, chlorite, spinel.

:y

B. Uherai With Hoh-Metallic Ldster

Streak — Hed, brown, yellow, or black

CrystalliiatioD Structure Crystals Massive

' Transparency

Bauxite

Never in crystala M — Pisolitic, oolitic, round disseminated grains, clay-like,

earthy

Knus, Dana, Pftnooa 94, 350, 34S

Dull

Earthy Opaque

Yellow Yellowish

brown

Lxhohite, V

Yelhiv oeher

Bog iron ore

Broum day

irotalone

—Earthy, porous, claylike, oolitic, pisolitie

Earthy

Dull

Opaque

YeUow Yellowish brown Dark brown

Wad

MnO„ H,0, etc.

Amorphous T

Dull

Brown

M— Earthy,

metimes

Blackish brown

with globular

Opaque

structure

Greaay

Lemon yellow-

C— Rare

Pearly

M— Foliated,

granular,

Translucent

reniform,

fibrous.

Monoclinic

Resinous

Reddish yel-

Transparent to

low

M— Compact,

granular,

translucent Greasy

Orange yellow-

Orthorhombic

Straw yellow

C— Pyramids

tabular

Honey yellow

M~Granular,

fibrous

Translucent

Brownish

earthy, crusts, compact

Reddish yellow

4. YELLOW OR BSOWH IN COLOR Hudness 1 to 3

Cleavage Fracture -F Tenacity

Specific i Gravity

Color and streak variable, due to pigments. Clay odor, when breathed upon. Commonly with pisolotic or oolitic structure. With clay or kaolinite, in nodules, grains, or irregular ma.iRes in limestone or dolomite.

Yettoiv ocher, earthy, and yellow, when impure gritty; brown ocher, earthy and brown ;6oj iron ore, porous; brown clay ironstone, massive or concretionary, impure from clay, saod. Ocherous varieties may soil fingers.

Very soft varieties soil fingers. Apparently very light and floats on water, due to porosity; usually adheres to tongue. With pailomelane, rhodochrosite, pyrolusite, limonite.

Lemon yellow

C— Clinopinaeoida 1 , usually conspicuous

Slightly sectile, laminie flexible

Orange yellow

C— Clinopinaeoida 1,

basal, not conspic-

F— Conchoidal Slightly sectile

Pale yellow

C— Indistinct F— Conchoidal Brittle

Characteristic lemon yellow color. Frequently disseminated in clay or dolomite. With realgar, stibnite, barite, calcite.

Redder in color than orpiment. Diaseminatd in clay or dolomite. With orpiment, stibnite, native arsenic, pyrite, barite, calcite.

Independent beds in gypsum, limestone; in lava, result of volcanic exhalations. With celestite, anhydrite, aragonite, clay, metallic sulphides.

:y

B. imiERALS WITH HOII-MBTALLIC LUSTER

Streak— Red, brown, fcUow, or black

CrTstallization Structure Crystals -C Massive— H

Traospareocy

Monoclinic

Pearly

Sulphur

C— Tabular, six-sided.

Dull

yellow

rare

Translucent to

Greenish

Mow.

H — Granular, scales,

opaque

yellow

Kiaua

niimi

Panon

„ powder

Brownish

S35.

yellow

Hexagonal

Dull

Reddish

brown

HgS

thick tabular, rare M— Fine granular, fibrous, earthy

Translucent to transparent

34

coatings

♦Olivenite

Orthorhombic

Vitreous

Brown

C— Priematic, acicular

Dull

M— Renitorm, fibrous, . with velvety surface;

Transparent to opaque

earthy

Wulfenite

Tetragonal

Greasy

Wax yellow

C— Square, thin tabular;

Adamantine

Orange yelloB

more rarely pyramidal

Transparent to translucent

Brown

H— Coarse, fine grained

Vanadinite

Hexagonal

Greasy

Straw yeUow

C— Prismatic, Bmatl, at

Translucent to

Brownish

times skeletal H — Compact, globular.

opaque

soo.

2S4

fibrous, crusts

brown

Streak — Red, brown, yeUow, or black

Hexagonal

C— Small, rare

H — Earthy coatings

Adamantine Honey yellow Greasy Orange yellow

Translucent Greenish yellow

:y

Hardness 1 to 9

Cleavage Fracture — P Tenacity

C— Pinacoidal F — Earthy, scaly Brittle

Disagreeable metallic taste. Oxidation product of iron sulphide minerals — pyrite, marcasite, pyirhotite.

Reddish brown C — Prismatic, not conspicuous F — Uneven Brittle to sectile

Dark color and streak due to impurities. High specific gravity often reduced by gang lie. Dissemioated in silicious rocks. With native mercury, pyrite, marcasite, realgar, stibnite.

Some varieties soil finers. Divergent, fibrous structure, and velvety surface important. With copper minerals.

Square plates, sometimes with forms of the third order. With lead minerals — galena, pyromorphite, vaoadinite.

C— None

F— CoDohoidal, i

Crystal faces smooth with sharp edges. With lead minerals, but never in large quantities.

Hardness over 3

—Prismatic, basal, not conspicuous

Usually as bright yellow powder on sphalerite. With smithsonite, prehnite, galena, calcite.

B. MINERALS WITH HOIT-METALLIC LUSTER Streak — Red, brown, jrellow, or black

Crystallization

Name, Compoeition, and

SUucture

Luster

Color

References

Crystals -C

Transparency

Massive -M

LmOHITE, varieties

C — Always pseudo-

Metallic

Yellowish

Compact

morpha, commonly

Dull

brown

Bog I

ran ore

after pyrite, marca-

Opaque

Dark brown

Brown clay ironstone

site, Biderite M— Compact, atalactitic,

botryoidal, nodular;

often with internal,

Moeea

radial fibrous struc-

Kraus

and

ture; porous, pisoli-

S5.

tic, oolitic

Siderite

Hexagonal

Vitreous

C— Rhombohedral,curved

Pearly

Reddish

or saddle-shaped

DuU

brown

M— Cleavable, granular,

Translucent

Dark brown

compact, botryoidal.

to nearly

35S,

rarely fibrous

opaque

Halerite

Cu"bic

Greasy

C— Tetrahedral, common

Submetallic

ZnS

M-Cleavable, fine or

Transparent to

brown

coarse grained,

opaque

Reddish

compact

brown

Pyromorphite

Hexagonal

Greasy

Wax yellow

C— Prismatic, thick

Adamantine

Green yellow

tabular, rounded

Yellowish

and barrel-shaped

opaque

brown

acicular

M — Globular, reniform.

disseminated, crusts

'Zincite

Hexagonal

Adamantine

Orange yellow

C— Small, rare

Vitreous

Reddish

ZnO

M— Compact, granular, foliated

Translucent to

opaque

yellow

Xenotime YPO,

Tetragonal Greasy Yellowish

C — Pyramidal, prismatic Vitreous brown

H — Compact, dissemi' Translucent to Reddish nated, rolled grains opaque brown

Pale yellow

:y

4. YELLOW OR BROWH IN COLOR Hftrdness over 3

Hard-

Streak

Cleavage -C Fracture -F Tenacity

Specific Gravity

Characteristics and

Associates

F— Conchoidal, splinbrowa

tery, earthy Brittle

face and passing into soft, yellow 00 hgrous variety. Compact limonite, massive with fibrous structure, rather pure; bog iron ore,

massive or concretionary, impure from clay, sand.

Pale yellow

Curved crystals and rhombohedral

Yellowish

conspicuous

cleavage characteristic. In ore

brown

F-Conchoidal Brittle

deposits; beds and concretions in limestones and shales. With pyrite, chalcopyrite, galena.

tetrahedrite, cryolite.

Pale yellow

C~Dodecahedral,

Distinguished from siderite by

Light brown

usually conspicu- Brittle

crystallization, more greasy luster, and cleavage. Color and streak vary with impurities. Extensively in limestones. With galena, chalcopyrite, pyrite, rhodoehrosite, barite, fluorite.

Yellow

C— None

Common alteration product of

Greenish yellow

F— Conchoidal, un-lead

minerals. With galena

cerussite, mimetite, barite, limon-

4. Orange yellow 4.5 Reddish yelloi

Basal, sometimes

conspicuous F — Uneven Brittle

C — Prismatic FUneven, splintery Brittle

Recognized by associates. With calcite, franklinite (black), willemite (yellow to green), rhodonite (flesh red.) On exposure becomes coated with the white

Commonly as loose, disseminated, or attached crystals resembling zircon but softer. In granite, gneiss, with zircon; alluvial deposits.

:y

B. HUTERALS WITH IfOH-HETALLIC LUSTER

Strak— Red, brown, yellow, or black

Structure Crystals— C Massive M

Transparency

Orangite, (Thorite) Tetragonal Greasy Orange yellow

C — Square prisms with Vitreous Brownish

ThSiOj bipytamids Transparent to yellow

Kriiua, Dana, Panons H— Compact, diasemitranslucent Dark brown 80. 430, 254 nated

Wolframite

Orthorhombic

Adamantine Yellow

C— Small, thin tabular. Dull Yellowish

needle-like; parallelly Translucent to brown grouped or in scaly, opaque Dark brown

fibrous, velvety crusts H — Reniform, stalactitic

Uonoclinic Greasy Reddish

C — Long fibrous, bladed, Submetallic brown

stalky; often diver- Translucent to Hair brown

gent, without good opaque Pale yellow terminations H — Compact, lamellar,

Monoclinic Submetallic Reddish brown

C — Thick tabular, short Opaque Bark brown

columnar, often large H — Bladed, curved lamellar, granular, com-

Monoclinic C— Tabular, rare M-— Compact, granular, bladed, disseminated

Greasy Dark brown

Submetallic Blackish

Translucent to brown opaque Yellowish

brown

Orthorhombic Adamantine

Only in crystals, — py- Metallic

prismatic, tabular

Uncoinmon color.

4. YELLOW OR BROWIT Dl COLOR HardneBS over 3

Cleavage Fracture -F Tenacity

Characteriatica a AsBociates

4.6 Light orange CPriematic, no

F — Concltoidal

Brittle

Yeilow orangite sometimes surrounded by dark brown to black thorite, which is thought to be decomposed orangite.

CBrachyjuoaeoidal P — Uneven, splintery Brittle

Usually with other iron minerals; in cavities in hematite or limonite. Crystals and cleavage distinguish it from limonite.

C-Clinopinacoidal,

conspicuous Brittle

Structure, cleavage, and high specific gravity characteristic. In quartz veins. With wolframite, fluorite, pyrite, scheelite, galena, tetrahedrite.

Reddish brown Dark brown

C— Clinopinaeoidat,

F— Uneven Brittle

Distinguished from huebnerite by streak. Powder may be slightly magnetic. With cassiterite, quartz, mica, apatite, soheelite,

Pale brown Grayish brown

C -Indistinct

al Brittle

Often covered with yellowish or

DiHseminated in acid igneous rocks; also in limestones. With magnetite, epidote, quartz, (eldspar.

Yellowish Brownish

C— Indistinct F— Uneven Brittle

Crystals may be striated; not twinned Uke rutile. With anataee, titanite, rutile, adularia.

B. HniERALS WITH nOH-HETALLIC LUSTER

Streak— Red, brown, yellow, or

and

Structure

Luster

Color

Crystals -C Massive -M

Transparency

Rotile

Tetragonal

Adamantine

Reddish brown

C— Prismatic, vertically

Submetallic

Yellowish

TiO, or TiTiO,

striated ; twinned

brown

yielding knee-shaped

opaque

Dark brown

Mosea

or roHette forms

Kiaiu, Dana

M— Compact, disseminated

Tetragonal

Adamantine

Reddish

C— Thick prismatic;

Greasy

Yellowish

SnO, or SnSnO.

knee-shaped twins

Dull

brown

quite common

Translucent to

Dark brown

H — Reniform. botryoidopaque

al, rounded pebbles.

often with internal,

radial fibrous structure

.— mood tin

SPIHEL, variety

Cubic

Vitreous

Yellowish

Picoiile

C— Octahedral, small

Dull

brown

M— Compact, granular.

Nearly opaque

Greenish Brown

1S7. 338.

Streak-

-Uncolored, white, or Eght gray

Cubic

Waxy

C— Rare

Greasy

Brownish

M— Wax-like crusts and coatings; stalacritio, dendritic

Transparent to translucent

Orthorhombic

Vitreous

C — Pseudohexagonal,

Dull

MgCl,,KCl,6H,0

rare

Transparent to

H — Compact, granular

translucent

Pjrrophyllile

Orthorhombic ?

Greasy

Brownish

CIndistinct

Dull

H,Ali,0„

M— Radiated fibrous, or lamellar aggregates;

Translucent to opaque

granular, compact

4. YELLOW OR BROWH m COLOR Hardness c-ni 3

Cleavage Fracture — F

Tenacity

Specific Gravity

Pale yeUow Pale brown

C— Prismatic, pyramidal, not conspicuous

F— Uneven

Brittle

Pale browQ Pale yellow

C— Indistinct F— Uneven Brittle

Characteristics and

Not as heavy as caasiterite. Often in fine hair-like inclusions. With quartz, feldspar, hematite, ilmenite, chlorite, brookite.

Recognized by high specific gravity. In veins cutting granite, gneiss; in alluvial deposits as stream tin. With quartz, mica, wolframite, arsenopyrite, molybdenite, tourmaline, fluorlte.

C- — Indistinct F— Conchoidal Brittle

Commonly in basic igneous rocks, especially olivine-bearing types.

With serpentine, olivine, corundum, magnetite, garnet.

C— None FConchoidal

Highly sectile

C — Indistinct F — Conchoidal Brittle

Cuts like wax, yielding shiny sui faces; on exposure turns violet, brown, or black. With silver minerals, especially argentite, native silver; also limonite, calcite, barite.

Bitter taste. Absorbs moisture. With halite, kieserite, kainite, sylvite, anhydrite.

C — Longitudinal F— Fibrous, uneve Laminee flexible

Soft and greasy like talc, but usually in radiating fibers. In schistose rocks. With cyanite, lazulite, topaz, graphite.

HOtERALS WITH HON-UETALUC LUSTER Streak — Uncolored, white, or light gray

Name, Composition,

and

Structure

Luster

Color

References

Crystals -C Massive -M

Transparency

C&lomel

Adamantine

C— Tabular, pryamidal.

Translucent to

Brown

H?,C1,

small

Mwea

H— Coatings

opaque

Kiaua, Dans

Paraona

Amorphous

Vitreous

M— Porous, earthy, chalk-

Dull

Yellowish

8iO,,xH,0

like

brown

8S. 329

opaque

Brown

Monoclinic

DuU

Yellowish

C — Scaly, hexagonal or

Pearly

H.Ali,0.

orthorhombic out- Une, rare M— Compact, friable.

mealy, clay-like

Earthy Opaque to translucent

TALC, variety

Monoclinic

Greasy

Yellowish

Soapatone or

atealite

M— Compact, globular.

Peariy

H,Mgi.O„

granular

Translucent to opaque

brown Browniah

m

Asbestos, variety

Orthorhombic ?

Silky

Yellowish

M— Fibrous, coarse or

Greasy

Brownish

H,Mg,8i,0,

fine; felted

Opaque

variety

Monoclinic

Silky

M— Fibrous, coarse or

Dull

Brownish

Silicate of Ca, Mg, Fe,

Al, etc.

fine; felted; compact, leather-or cork-like

Opaque

HardoeBS 1 to 3

Cleavage — C Fracture Tenacity

Characteristics and

White Gray

C — Indistinct F — Conclioidal Very sectile

Cliaracterized by high specific gravity and associates. With mercury minerals — cinnabar, native mercury; barite, quart*, tetrahedrite.

1. White 2.e Gray

2.6 Yellowish white P— Earthy Brittle

Apparently very soft, but fine particles scratch glass. Resembles kaolinite, but gritty and not plastic.

Not gritty like tripolite. Very strong clay odor when breathed upon. Usually adheres to tongue and becomes plastic when moistened. Greasy feel. With quartz, feldspar, corundum, dia- Bore, topas.

2.6 Greasy or soapy feel important.

2.8 SoapsUme or sUatiU, coarse to fine granular, more or less impure. Hardness varies. With serpentine, chlorite, dolomite magnesite, actinolite.

1 . Delicate, fine, parallel, flexible

2 . 5 fibers, easily separable, Aori

fibered asbesloi, compare below.

In veins or seams in compact

serpentine.

F— Fibrous Flexible, tough

Long fihered asbestos, parallel, flexible fibers. Compare above. Mountain leather, mountain eork, mountain wood, compact but light and tough.

:y

B. HnmRALS WITH ITOH-HETALLIC LUSTER

Streak— Dncolored, white, or gray

Crystal Usatioi Structure Crystals Massive M

Transparency

Sal Ammoniac NH.Cl

C — Distorted, rare H — Fibrous, powdery, stalactitic, crusts

Vitreous Yellow

Trausparent to Yellowish translucent brown

Stnivite

NH,MgP0,.6H,0

Orthorhombic CDomatic, hemi-morphic

M — Granular, earthy

♦SODA HTIER (Chile saltpeter) Hexagonal C— Rare NaNO, H— Granulai

GYPSUli varieties

Selenite CaSOj,2HjO Satinspar Ordinary

Vitreous Brownish

DuU Yellowish Translucent to

opaque

Vitreous Yellowish

Transparent Lemon yelloir Reddish brown

Pearly Yellow

Vitreous Honey yellow

Silky Brown

Dull

Transparent to opaque

Adamantine Straw yellov

Greasy Brownish

Translucent yellow

Reddish

yellow

Monoclinic

C — Tabular, prismatic; swallow tail twins

M— Cleavable, coarae and fine grained, fibrous, foliated,

Orthorhombic

C— Pyramidal, tabular

H — Compact, granular,

fibrous, earthy,

Cubic Vitreous Yellow

C — Cubes, alone or with Transparent to Reddish

octahedrons, rare translucent yellow H — Granular, compact

Cubic Vitreous Yellow

C — Cubes, often skeletal Transparent to Yellowish

or hopper-shaped translucent brown

M— Compact, cleavable, Brownish

granular, fibrous,

stalactitic, crusts

:y

4. YELLOW OR BROWH m COLOR Hardness 1 to 3

Cleavage

Streak

Fracture -F Tenacity

White

C— Octahedral, indistinct F— CoDchoidftl Brittle

White

C— Pinacoidal

Brittle

White

C— Rhombohedral

F— Conchoidal Brittle

White

C — CI inopinacoidal,

conspicuous; pyramidal, orthopinacoidal F — Conchoidal, fibrous Brittle, lamins flex-

Specific Gravity

2.6 Yellowish white F— Conchoidal

Brittle

C— Cubic F— Conchoidal Brittle

C — Cubic, perfect,

conspicuous F — Conchoidal Brittle

Pungent, salty taste, somewhat astringent. Usually sublimation product. Near volcanoes, burning coal beds, guano deposits.

Crystals coffin-shaped with pronounced hemimorphiam. In sewers, vaults, guano deposits.

Cooling and saline taste. Absorbs moisture readily. In deposits with gypsum, sand, clay, guano.

Selenite, crystals and cleavable plates, usually transparent; atin spar, fibrous with silky luster; ordinary, granular. In lime stones and shales. With halite, celestite, sulphur, aragonite, anhydrite; ore deposits.

Independent beds in gypsum limestone in laa result of \ol came exhalations W ith cries tite anhydrite aragonite clay metallic sulphides

Color due to impurities bait bitter taste May absorb mois ture and become damp In salt deposits With hate kainite cirnalhte

Pigment usually iron oxide May absorb moisture and become damp Characteristic cubical cleavage and sahne tiste With shale gypsum anhydrite pol>

:y

B. BDHERALS WITH IfOH-HBTALUC LUSTER Streak — Dncolored, white, or Ugbt gny

Structure

Luster

Crystals -C Massive -M

Transparency

Paragonite

Monoclinic

M — Compact, fine scaly

Pearly Translucent

Yellowish

aggregates

Eraiu, Dana.

Vitreous

Light yellow

C — Tabular, pyramidal,

Pearly

Yellowish

with orthorhombic

brown

or hexagonal outline;

translucent

Light brown

often large and rough

y

Mcales, plates; toU-

ated and plumose

aggrfgatee

Pearly

Yellow

C— Prismatic, tabular,

Yellowish

with hexagonal or

Transparent to

brown

orthorhombic outline;

translucent

Brown

often large and

M— Plates, disseminated

scales

APATITE, variety

Phosphate rock chiefly

Hexagonal

M— Compact, fibrous,

nodular, reniform,

earthy

DuU

Opaque

Brown

2S3. 401.

Monoclinic

C— Fine, acicular

H— Fibrous, lamellar

SUky

Translucent to opaque

Brownish

Glsuberite

NaO.,CaSO.

Monoclinic

C— Thick tabular

H— Reniform, lamellar

Greasy Vitreous Transparent to

Pale yellow YeUow

Monoclinic

C— Tabular, pseudohexagonal

; twins and

trillings M— Compact, lamellar

Greasy

Transparent to

YeUow Brown

Hardness 1 to 3

Cleavage — C Fracture — F Tenacity

C — Basal, perfect F — Scaly, granular Tough

Distinguished from other micas

by associates — cyaDtte, stau route, tourmaliDC.

C — Basal, perfect,

conspicuous Tough, laminie very

elastic

C — Basal, perfect, conspicuous

Tough, lamina very elastic

Lighter colored than phlogopite. Structure, perfect cleavage, and elasticity important. Crystals may show distinct partings perpendicular to cleavage — ruUd mica. In granitic rocks, schists, limestones. With feldspar, quartz, tourmaline, beryl, garnet.

Usually amber brown or bronie in color. When cleavage lamina are held close to the eye in viewing a source of light a star-like form is sometimes observed. Especially characteristic of crystalline limestones, dolomites, schists. With pyroxenes, amphiboles, serpentine.

White White

F— Conchoidal, Brittle

nn- 3

More or less impure masses, frequently resembling compact

nodules, concretions.

S.

C— Fibrous Brittle

Usually with quarti, magnetite, scAtrt.

White

C— Basal

F— Conchoidal Brittle

Bitter, saline taste. On exposure becomes coated with white powdery crust. With halite, thenardite, mirabilite.

White

C— Basal, perfect P— Conchoidal, ra

observed Rather sectile

rely 6

Soft and very heavy. Twins and trillings resemble those of aragonite. Sparingly with lead min-calcite

, galena.

B. Hiherals With Koh-Metallic Ldster

Strfeak — Uncoloied, white, or Ught gray

Cryatallizatioi Structure Crystals — C Massive— M

Transparency

Amorphous

Greasy

Light yellow

H — Irregular, atalactitic,

Honey yellow

C.,H,.0.

. grains, lumps

translucent

Bronnisb

yellow

KrauB, Dans.

Kainite

Monaclinic

C— Tabular, prismatic,

Vitreous Transparent to

Yellow

Mg80,.KC1.3H,0

rare M— Compact, fine

translucent

grained

Monoclinic

C— Pseudohexagonal,

Vitreous Pearly

Yellowish

tabular, rare M— Stalactitic, mammillary, surface smooth, internal structure fibrous; scaly aggre-

Translucent

gates

Cryolite

Vitreous

Grayish

C— PBCudocubical, small.

Greasy

brown

AIF,.3NaF

M— Cleavable, compact, granular

translucent

Dark brown

Orthorhombic

Vitreous

C— Tabular, prismatic.

Pearly

Brownish

very common; crested divergent groups M— Compact, lamellar, fibrous, cleavable.

Transparent to opaque

Dark brown

31B

reniform

Amorphous

Vitreous

Brown

M— Reniform, mammil-

Greasy

Yellow

AliO. 5H,0

lary, stalactitic, in-

Translucent

Monoclinic

Kieserite

Vitreous

Yellow

C— Pyramidal, rare

Transparent to

MgSO,.H,0

H — Compact, granular

translucent

Vnconuuon color.

Cleavage — C Fracture -F

Tenacity

Specific Gravity

Characteristics and

Fossil resin. Electrified rubbed. Often mottled

striped. Sometimefi with inclu' lions — ineectB, vegetable Uquids, minerale.

2.S

White

C— Pinacoidal, pris-

Taste, salty, bitter and astringent.

matic, not conspicuous F— Uneven

Brittle

Non-hygToBcopic, With halite, sylvite.

White

C— Indistinct

Strong clay odor when breathed

Tough

upon. With bauxite, natrolite, Hmonite, corundum.

2.S

White

Often contains disseminated

perfect, nearly at

conspicuous F — Uneven Brittle

siderite, chalcopyrite, galena, pyrite, fluorite, coiumbite.

White

C— Basal, prismatic.

Characterized by rather high

usually conspic-

F— Uneven Brittle

specific gravity and cleavages. In metalliferous veins ; pockets, lenticgalena

, sphalerite, fluorite, chalcopyrite; manganese and iron minerals.

White

F-Conchoidal,

earthy Brittle

Structure resembles opal. In fissures and cavities with iron and copper minerals.

White

C— Pyramid

Due to absorption of water,

F— Granular

becomes coated with white crust

Friable to firm

of epsomite. With halite, po-

B. Bokerals With Moh-Hetallic Luster

Streak

— tlncolored, white, or light gray

Straetiire

Luater

Crystals -C Massive -M

Transparency

CALCITE, varieticH

Vitreous

Honey yeUow

Dog tooth spar

C— Scalenohedral, rhom-

DuU

Yellowish

CaCO, Nail head ipar

bohedral, prismatic;

Transparent

brown

tabular, acicular;

to nearly

Dark brown

Ltmentone

may be highly modi-opaque

Marble

fied and twinned

H — Cleavable, granular,

fibrous, banded, stalactitic

, oolitic, porous

, compact, crusts,

KraiB. Dsna, Panmn,

Wulfenlte PbMoO.

Tetragonal Greasy Wax yellow

C— Square, thin tab- Adamantine Orange yello

ular; more rarely py- Transparent to Brown

ramidal translucent

H — Coarse, fine grained .

Hexagonal

C— Prismatic, small, at

times skeletal H— Compact, globular,

fibrous, crusts

Greasy Straw yellow

Translucent to Brownish opaque yellow

Reddish

Streak — Cncofcired, white or light gray

Polyhalite

Monoclinic

Vitreous

Yellowish

C — Pseudohexagonal,

Peariy

tabular, rare

Translucent

M— Stalactitic, mammillary

, surface smooth.

internal structure

fibrous; scaly aggregates

Monoclinic 7

Greasy

Yellowish

C— Indistinct

Pearly

M— Compact, fibrous.

lamellar

HaidjiMs 1 to3

Cleavage - Fracture — Tenacity

Characteristics and AsBociatea

-— Rombohedral, usually eonspicu-

Often in extensive deposits. Rhombobedial cleavage characteristic eapecialiy on crystals. Cleavage surf aces often striated. Very strong double refraction easily observed when transparent. To distinguish varieties, see references.

Whit* C — Pyramidal, indis-

Yeliowish white tioct

F— Conchoidal, un-

Square plates sometimes with forms of the third order. With lead minerals — galena, pyromorphite, vanadinite.

Crystal faces smooth with sharp edges. With lead minerals, but never in large quantities.

Hardness 3 to 6

C— Indistinct Tough

Strong clay odor when breathed upon. With bauxite, natrolite, limonite, corundum.

Taste, bitter and astringent, but weak. With halite, anhydrite, 1, clay.

:y

HnrERALS WITH HOH-HETALUC LUSTER Streak — Uncolored, white, or light gray

Crystallizatiol Structure Cryatala-C Klussive - M

E Orthorhombic

C— Tabular, priBmatic, common; pyramidal HoMB H— Compact, cteavable, . Dana. PaSona fibrous, granular,

Transparency

Vitreous Yellow

Pearly Yellowish Transparent to white translucent

Vitreous

Yellowish

C— Tabular, prismatic,

Pearly

Brownish

Transparent to

Dark

ed and divergent

opaque

brown

groups

H — Compact, lamellar,

fibrous, cleavable,

reniform .

♦Ahglesite

Orthorhombic

Greasy

Yellow

C— Prismatic, tabular,

Adamantine

Brown

pyramidal M— Compact, granular, nodular

Transparent to opaque

2se

*Cerdssite

Orthorhombic

C— Tabular, prismatic.

Greasy

Yellowish

pyramidal; pseudohexagonal; clusters and etar-shaped groups M— Interlaced bundles, granular, stalactitic,

Silky ,

Transparent to translucent

brown

compact

Heulandite

Vitreous

Brown

C— Tabular, striated

Peariy

Yellow

H — Foliated, granular,

Transparent to

globular

S

s

Vitreous

Yellowish

C— Twinned, sheaf-like,

Pearly

Yellowish

N

6H0

radial, or globular

Transparent to

brown

aggregates

Brownish

Hardness 3 to 6

Cleavage Fracture -F Tenacity

Specific

C — Basal, prisma tic,

conspicuous F — Uneven

Brittle

Prominent cleavages. Heavier than calcite, lighter than barite. In limestneB, dolomites, shales. With sulphur, gypsum, aragonite, halite, galena, sphalerite.

—Basal, prismatic, usually conspicu-

F— Uneven Brittle

Characterized by rather high speciRc gravity and cleavages. In metalliferous veins; pockets, lenticular masses in limestone. With galena, sphalerite, fluorite, chalcopyrite; manganese and iron minerals.

C — Basal, prismatic F— Conchoid al Brittle

Adamantine luster and very high specific gravity important. Distinguished from cerusaite by absence of twins. Oxidation product of lead minerals. Usually in cracks and cavities. With galena, cerussite.

White

C— Indistinct

Twinning, structure, luster, and

Gray

specific gravity characteristic.

Brittle

With lead mmerab— galena, pyromorphite, anglesite; also

C — Clinopinacoidal ,

perfect FUneven Brittle

C — Indistinct FUneven Brittle

In basic igneous rocks and metalliferous veins. With chabasite, Btilbite, apophyllite, datolite.

Radial and sheaf-like structure important. In basic igneous rocks and ore deposits. With heulandite, chabazite, apophyllite, datolite, calcite.

B. HUfERAIS WITH HOH-BIETALLIC LUSIGR

Streak

-Uncotored. white, or light paj

Structure

Luster

Color

Refereneea

CryrtaU-C Hamive -H

Transparency

Monodinic

Vitreous

C — ColumnBr

Dull

Brownish

H— Radial, divergent,

Transparent to

earthy

opaque

Mora

KrauB, Dana,

Orthorhombic ?

Greasy

Greenish

C— Unknown

Waxy

brown

H,Mgi.O.

H — Compact, columnar,

Translucent to

Greenish

fibroua, lamellar,

opaque

granular

Yellowish

brown

Monoclinic

C— Six-sided scales.

Pearly Vitreous

H,CaAli,0„

plates H— Scaly, platy; foliated,

granular aggrctes

APATITE, variety

Hexagonal

Dull

Brown

PkoaphaU rock

M— Compact, flbrous,

Opaque

CaCPOJ chiefly

nodular, reniform

Orthorhombic

Vitreous

Yellow

C-Capillary, smaU

Translucent

Brown

M— Crusts, globuUr, hemispherical aggregates, with radial fibrous

structure

Hexagonal

Vitreous

Transparent to

brown

- curved surfaces H — Coarsely crystalline, compact, granular.

translucent

Grayish brown Dark brown

friable

Unoommon color.

Hardness S to 6

Cleavage Fracture "F

Tenacity

Specific

Gravity

F — Uneven, earthy

Brittle, friable

On exposure becomes dull and crumbles to powder. In cavities and fisBuiea in basic igneous rocks. With atilbite, analcite. apophyllite, native copper.

F — Conchoidal, splin

tery Brittle

Smooth and greasy feel. Oftn spotted, clouded, multiHiolored.

Sometimes crossed by seams of asbestos (chrysotile). With magnesite, chromite, gamierite, pyrope, platinum, calcite.

C — Basal, perfect, conspicuous

F— -Scaly, granular Brittle

Resembles the micas in structure and cleavage, but harder; lamins brittle and inelastic. With chlorite, emery, diaspore, coin-

F— Conchoidal, Brittle

More or less impure masses, frequently resembling compact, brown limestone. Independent beds, nodules, concretions.

CKnacoidal,

domatic F — Uneven, fibrous Brittle

Secondary mineral occurring on surfaces of rocks or minerals, as crystalline crusts with pronounced radial fibrous structure.

White

C— Ehombohedral,

Gray

F — Conchoidal

Brittle

Crystals generally curved or saddle-shaped. Marble includes some compact varieties. Independent beds; in fissures and cavities; with ore deposits.

:y

B. UKERALS WITH ITOH-METALUC LUSTER StreakDncolored, white, or light gray

*Scorodite FeAsO. 2H,0

nd Structure

Color

Crystals -C

Transparency

! Massive -M

Orthorhombic

Vitreous

Wine yelk

C — Chisel-or spear-

Resinous

Transparent to

brown

translucent

Mosea acicular aggregates

Pam M— SUlactitie, reniform,

Pyrohorphite

Uncommon color.

Orthorhombic Vitreous

C— Prismatic, pyramid!, Greasy

dnisy Translucent H — Botryoidal, fibrous,

Orthorhombic

Vitreous

C— Spear-shaped, colum-

Greasy

Yellowish

nar, acicular; often

Transparent to

brown

in divergent groups

Brown

H — Granular, compact,

botryoidal, fibrous

Hexagonal

Vitreous

Light brown

Pearly

Reddiah

curved or saddle-

Dull

brown

shaped, common

Translucent

Dark brown

H — Cleavable, granular.

to nearly

compact, botryoidal,

opaque

rarely fibrous

Cubic

Greasy

Honey yellow

C— Tetrahedral, common

Yellowish

M— Cleavable, fine and

Translucent to

brown

coarse grained, com-opaque

Reddish browi

pact

Hexagonal Greasy Wax yellow

C — Prismatic, thick tab- Adamantine Greenish

utar, rounded and Translucent to yellow

barrel-shaped; actcuopaque Yellowish

lar brown H — Globular, reniform, disseminated, crusts

:y

HardneBB 3 to 6

Cleavage — C Fracture -F Tenacity

Characteristics and Asaociates

C— Pinacoidal, pris-

Twins common, often pseudohex-

Gn.y

matic F— Conchoidal Brittle

agonal— prism and striated base. In cracks and cavities; with ore deposits; deposition from hot springs; in shells. With gypsum, celestite, sulphur, siderite, zeolites.

White

C— Indistinct

Grayiflh Brownish white

F— Uneven, conchoidal

Brittle

ite, pyrite.

3.G

White

C— Prismatic, indis-

Structure similar to aragonite.

Gray

tinct F— Uneven

Brittle

Divergent columnar masses and higher specific gravity characteristic. In ore deposits; independent beds. With galena, barite, calcite.

3.G

Gray

C— Rhombohedral,

Distinguished from sphalerite by

White

conspicuous F — Conchoidal Brittle

curved crystals and rhombohedral cleavage. In ore deposits; beds and concretions in limestones and shales. With pyrite, chalcopyrite, galena, tetrahedrite, cryolite.

White

C— Dodecahedral,

Yellowish white

usually conspicu-

F— Conchoidal Brittle

portant. Color and streak vary

limestones. With galena, chalcopyrite, pyrite, barite, fluorite, rhodochrosite.

3.B White C— None

4. Yellowish white F— Conchoidal, i

Common alteration product of lead minerals. With galena,

ceruBsite, mimetite, barite, limon-

B. Hdierals With Hoh-Hetallic Lustek

Streak

— Dncolored, white, or light gray

Name, Composition, aad RefereocM

Structure

Crystals -C Massive -M

Luster Transparency

Color

Mimetite

Hexagonal

C— Priamatic, tabular,

rounded, barrel-sh

&ped H — Globular, reniform,

Greasy

Adamantine Tranalucent

Orange yellow YeUowiah brown Brown

RHODOCHROSITG MnCO,

Hexagonal

C— Rhombohedral, rare

M— Cleavable, granular,

compact, botryoidal,

Vitreous

Yellow Brown

MAGHESITE MgCO,

Hexagonal

C— Rhombohedral, rare

Vitreous

DuU

Translucent

to opaque

Yellowish Grayish brown

Cubic

C— Cubes, alone or modified, well developed

M— Cleavable, granular, fibrous

Transparent to nearly opaque

Wine

Brown

*CHABAZITE CaAli,0„.8H,0,

etc

Hexagonal

C— Rhombohedral, cubelike, lenticular M— Compact

Vitreous Translucent to tranaparent

YeUowish Brownish

BaAli.0„.6H,0

etc.

Monoclinic

C— Usually twins, penetrating at 90°

Vitreous Translucent

Yellowish

Brownish

Xenotime YPO.

Tetragonal

C — Pyramidal, prismatic

nated, rolled grains

Greasy Vitreous

opaque

YeUowish brown

Pale yellow

i. YELLOW OR BROWN IN COLOR

Cleavage —C Fracture — F Tenacity

White

C— Pyramidal, indis-

Yellowish white

tinct F— Uneven

Brittle

as common. With lead minerals —galena, pyromorphite.

White

May turn brown to black on

Gray

conspicuous F-Uneven Brittle

exposure due to MnO,. With ore lena, sphalerite, pyrite, alabandite

, psilomelane, silver minerals.

White

C— Rhombohedral

Conchoidal fracture generally

S.

(crystals) F— Conchoidal, con- . spicuous

Brittle to tough

apparently very hard. In talcose and chloritic schists, serpentine, gypsum; independent deposits

.

White

C— Octahedral, per-

3,

Recognized by crystal form.

octahedral cleavage, and hardness

. Common gangue of metallic ores, especially galena, sphalerite, caB8itrite; also withcalcite, barite.

White

Generally in cube-like crystals.

not conspicuous F— Uneven Brittle

Inferior cleavage distinguishes it from fluorite and calcite. In basic igneous rocks. With ana!- cite,stilbite,harmotome,laumonl

White

C— Pinacoidal

ite, heulandite.

Cruciform twins. In basic igneous

Brownish white C — Prismatic Yellowish white F— Uneven, splintery Brittle

rocks and metalliferous veins. With chabazite, calcite, quartt, adularia. PhiUipiite, contains calcium replacing barium. Commonly as loose, disseminated, or attached crystals resembling zircon, but softer. In granite, gneiss, with zircon; also in alluvial deposits.

:y

B. Uherals With Hoh-Icetallic Luster

Streak

Name, CompOBition, and

Structure

Luster

Color

References

CrystalB -C Massive -M

Transparency

Tetragonal

Greasy

Pale yellow

C— Pyramidal, small,

Adamantine

Yellowish

more rarely tabular

brown

H — Druay crusts, reni-translucent

Grayish brown

Kreip, Dam.,

Pa'Sn.

form, granular, com-

33S

pact

tabu-

Monoclinie

Yellowish

la

C— Tabular, prismatic

Silky

Brownish

M— Cleavable, fibrous, granular, compact

translucent

Apatite

Hexagonal

Greasy

Brown

C— Prismatic, thick tab-

Vitreous

Greenish

ular, sometimes

Translucent to

brown

large, with

opaque

Reddish brown

H— Compact, fibrous.

Yellow

nodular, reniform

Orthorhombic

Vitreous

Yellow

C— Thin tabular, pyram-

DuU

Yellowish

idal, hemimorphic.

Transparent to

brown

highly modified '

translucent

Brown

M— Compact, globular,

granular, stalactitic,

isa, 446,

cellular, earthy

Huebnerite

Monoclinie

Resinous

Reddish brown

C— Long fibrous, bladed,

Submetallic

Hair

stalky; often diver-

Translucent to

brown

gent, without good

opaque

Pale yellow

terminations

M— Compact, lamellar.

granular

Hexagonal

Vitreous

Brown

C— Small, usually as

Dull

Yellowish

druses or crusts

brown

M— Botryoidal, stalactitto

nearly

Orange

ic, fibrous, compact,

opaque

yellow '

cellular, granular

HardnessS to 6

Cleavage Fracture "F Tenacity

Characterietics and

C — Pyramidal, not

conspicuous F — Conchoidal, un-

C— Basal, orthopinacoidal

, perfect ¥ — Uneven Brittle

Small, well developed octahedrallike crystals, usually on quartz; when massive high specific gravity important. With cassiterite, wolframite, fluorite, apatite, molybdenite.

Fibers may be parallel or divergent. Typical contact mineral; often in crystalline timestones. With garnet, diopside, veau-viaoite, graphite.

Crystals may be vertically striated

and have fused appearance.

Color unevenly distributed, often

h g h p In crystal-

m m lliferouB de-gn

ka. With

ss fluorite, wol-

— Prismatic

— Uneven, conchoid-

-like groups

ties. When

B or cellular.

n b sphalerite,

pec lly smithson-

C— Clinopinacoidal,

conspicuous Brittle

tenstic. In

W h wolframite,

lite, galena.

White Gray

C— Rhombohed ral,

not often observed FUneven, splintery Brittle

Cellular varieties called dry bone. Often mixed with sand, clay, limonite, calcite. With zinc minerals, especially sphalerite, hemimorphite. Frequently pseudomorphous after oalcite.

B. HSfERALS WITH NOH-HBTALLIC LUSTER

Streak — Dncolored, white, or light

CiystallizatioQ Structure Crystals Massive — M

Luster Transparency

ralroUte Orthorhombic Vitreous

C — Slender prismatic, Silky

nearly square, radial Transparent to

Moees or interlacing groups translucent

Kraufl, Dana. Paraons M — Fibrous, granular, 277, 461, 416 compact

o

Orthorhombic

Vitreous

Yellowish

C— Prismatic, vertically

Silky

striated, divergent

Pearly

5H,0

groups M— Fibrous, columnar, radial; spherical con-

Translucent to transparent

27B, 462.

cretions, compact

Datolite

Vitreous

C— Prismatic, pyramid-

Greasy

Brown

dal, highly modified

M— Compact, fibrous,

granular, botryoidal

Dull

Translucent to opaque

Vitreous

Brown

C— Wedge-or envelope-

Greasy

Reddish

shaped when dis-

Transparent to

brown

Honadte

seminated; tabular opaque Yellow or prismatic when attached H — Compact, lamellar

Monoclinic Greasy Reddish

C — Thick tabular, square Vitreous brown

prismatic Transparent to Yellowish

M — Angular fragments, opaque brown

rolled grains Honey yelloi

Tanciinite Hexagonal

C — Prismatic, rare H,(Na„Ca)(NaCO,Ali,0„ M— Compact, lamellar, columnar, dissemi- 233. 411, 395 nated

♦ Uncommon color.

Greasy Yellow

Vitreous Brownish

Pearly yellow

Translucent to transparent

:y

4. YELLOW OR BROWN IH COLOR Hardness S to 6

Cleavage "C Fracture — F

Tenacity

Specific Gravity I

C — Prismatic, perfect Uneven Brittle

Crystals have nearly square crosssection. In basalts and phonolltes. With chabazit, analcit, apophyllite, stilbite, prehnite, datolite.

C — Pinacoidal F — Uneven

Brittle

When massive, radial fibrous, often mottled or banded. In fiasures and cavities in basic igneous rocks. With stilbite, analcite, prehnite, calcite.

C— -None FConchoidal, uneven

Brittle

— Prismatic, conspicuous parting often noted

F — Cone hold a 1

Brittle

Compact masses often with reddish, greenish, or whitish streaks and spots. In cracks and cavities in basic igneous rocks. With calcite, prehnite, epidote, native copper, zeolites.

With feldspars, pyroxenes, am- p h i b o 1 e s, chlorite, ecapolite.

F — Conchoidal,

Crystals commonly amall, highly modified; rounded grains in sand. With quarta, magnetite, zircon, garnet, thorite, gold, chromile, diamond.

Easily recognized by associates — nephelite, sodalite, biotite, feldspar, titanite.

B. HIHERALS WITH NOHrHETALLIC LUSTER

Streak — Uncolored, white, or Ught graj

Crystal!! nation Structure Crystals -C Massive M

elffiolite) C — Short prismatic, (Na,K},Ali,0„ tabular

MoBea H — Compact, dissemi'

Kraus, Dana, Parsons Dated grains

Greasy Yellowish

Vitreous Reddish brown

Transparent to Brown opaque

Orthorhombic Vitreous Grayish brown

C — Prismatic, rare Pearly Yellowish

H — Lamellar, columnar, Translucent brown

fibrous Clove brown

Enstatite

Orthorhombic

Vitreous

Grayish brown

C— Prismatic, rare

Peariy

Greenish

M— Fibrous, lamellar,

Translucent to

brown

columnar, compact

opaque

Yellowish

3S4

Brohzite

Orthorhombic

Bronsy

Bronze

C— Prismatic, rare

Silky

brown

M— Fibrous, lamellar.

Translucent to

Yellowish

compact

opaque

brown

Hypersthene

Orthorhombic

Pearly

Dark brown

fS

C— Prismatic, tabular,

Blackish

rare Translucent t

—Granular, foliated, opaque

cleavable aggregates

Monoclinic

C — Prismatic, thick

columnar, prism

angle sr H — Compact, granular,

columnar, lamellar

Vitreous Yellowish

Dull Brownish

Transparent to opaque

Rhodonite

Triclinic

Vitreous

Yellowish

C— Tabular', prismatic,

Dull

Brownish

rounded edges M— Compact, cleavable, granular, dissemi-

Translucent to' opaque

Hnrdnesa 3 to G

Cleavage -C Fracture — F

Tenacity

C — IndiBtinct F — Conchoidal,

Diatinguished from orthoelase by inferior cleavage and more greasy luster. With feldspars, cancrinite, biotite, Bodalite, corundum; not with quarti.

?hite C— Prismatic

Often with metallic achilles,

rayish F — Fibrous

resembling broniit* and hyper-

Brittle

sthene. Softer when altered. In crystalline schists. With talc, hornblende, mica.

white C— Prismatic,

pina-

Often softer due to alteration to

serpentine. Commonly in basic

Ous

igneous rocks. With olivine.

F — Uneven

chondrodite, serpentine, talc.

Brittle

/hite C— Priamfttic,

pina-

Cleavage surfaces usually fibrous

rayish coidal, conspicuor

lamellar, irregular or wavy.

ous

with distinct broniy luster;

F— Uneven

darker than enatatite. In basic

Brittle

igneous rocks.

/hite C— Pinacoidal

con-

Copper red iridescence often noted,

rayish spicuous